Ornithothoraces

Carinatae sensu Gauthier and de Queiroz, 2001
Definition- (keeled sternum homologous with Vultur gryphus)

Ornithothoraces Chiappe and Calvo, 1994
Definition- (Iberomesornis romerali + Passer domesticus) (modified from Chiappe, 1995)
Other Definitions- (Sinornis santensis + Passer domesticus) (Sereno, in pres; modified from Sereno, 1998)
= Ornithopectae Chiappe, 1991
Definition- (Iberomesornis romerali + Passer domesticus) (modified from Chiappe, 1991)
= Euornithes Stejneger, 1885
Definition- (Iberomesornis romerali + Passer domesticus) (modified from Sanz and Buscalioni, 1992)
Other definitions- (Passer domesticus <- Sinornis santensis) (Sereno, in press; modified from Sereno, 1998)
(Passer domesticus <- Enantiornis leali) (modified from Longrich, 2009)
= Ornithothoraces sensu Sereno, 1998
Definition- (Sinornis santensis + Passer domesticus) (modified)
Diagnosis- dentary teeth present (also in many non-ornithurines; absent in Alethoalaornis, Gobipteryx, "Gobipipus", Archaeorhynchus, Apsaravis and Aves); dentary not strongly forked posteriorly (also in many non-euavialans; absent in Dapingfangornis, "Gobipipus", Yixianornis + Songlingornis, Apsaravis and Palaeognathae); external mandiblar fenestra absent (also in Juravenator, Compsognathidae, Shenzhouraptor and Omnivoropterygidae; absent in Hebeiornis, Dapingfangornis, Yixianornis and many Aves); less than thirteen dorsal vertebrae (also in Harpymimus+Ornithomimus and Oviraptoriformes); scapulocoracoid mobily jointed (also in Rahonavis, Shenzhouraptor and Jixiangornis; absent in Ratites); distal end of posterodistal sternal process fused to sternum (absent in Liaoningornithidae, Cuspirostrisornis, Hesperornis and Ichthyornis); posterolateral sternal process extends posteriorly past median posterior edge of sternum (also in Yandangornis; absent in Jibeinia, Hebeiornis, Eoenantiornis and "Cathayornis" chabuensis); projected carina on sternum (also in Parvicursorinae; absent in Jibeinia, Longchengornis, Rapaxavis, Eoalulavis, Patagopteryx, Hesperornis and Ratites); interclavicular angle <68 degrees (also in Jixiangornis and Dalianraptor; absent in Hesperornis); capital groove developed on proximal humerus (also in Gallimimus, Neimongosaurus, Therizinosauridae, Mononykus, Deinonychus and Bambiraptor; absent in Elsornis, Apsaravis and Ambiortus); dorsal condyle of distal ulna developed as semilunate ridge (also in Heyuannia, Rahonavis, Anchiornis, Zhongjianornis and Confuciusornis zhengi; absent in Eocathayornis); less than four phalanges on manual digit III (also in Tyrannosauridae, Caudipteryx, Jinfengopteryx and Omnivoropterygidae); alula present (also somewhat developed in Microraptor).

Aberratiodontuiformes Gong, Hou and Wang, 2004
Aberratiodontuidae Gong, Hou and Wang, 2004
Aberratiodontus Gong, Hou and Wang, 2004
A. wui Gong, Hou and Wang, 2004
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (LHV0001a/b) skull (58.7 mm), mandibles, hyoid, eleven cervical vertebrae (88 mm), dorsal vertebrae, dorsal ribs, sacrum, caudal vertebrae?, pygostyle (24.5 mm), scapula (53 mm), coracoid (31 mm), furcula, sternum (55 mm), sternal ribs?, humeri (69 mm), radii (70 mm), ulnae (71 mm), two carpals, partial digit I?, partial metacarpal II, phalanx II-1, phalanx II-2, manual ungual II, partial digit III?, ilium (46 mm), pubes (43 mm), ischium?, femur (55 mm), tibiotarsi (66.7 mm), fibula, metatarsal I, pedal phalanx I-1 (8.7 mm), pedal ungual I, metatarsal II, phalanx II-1 (12.6 mm), phalanx II-2 (10.2 mm), pedal ungual II, metatarsal III (33 mm), phalanx III-1 (13.4 mm), rest of digit III, metatarsal IV (31 mm), phalanx IV-1 (8.4 mm), phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV (5.9 mm), feathers
Diagnosis- anterior four maxillary teeth much smaller than premaxillary or posterior maxillary teeth; elongate postorbital region; about twenty-four dentary teeth; scapula dorsoventrally curved; scapular acromion process short; sternum elongate; broad posterolateral sternal process with weakly expanded distal ends; manus shorter than humerus; postacetabular process broad; pubic boot absent.
Comments- This may be an enantiornithine less derived than Protopteryx or a taxon closer to Passer than Enantiornis, but outside Ornithuromorpha.
References- Gong, Hou and Wang, 2004. Enantiornithine bird with diapsidian skull and its dental development in the Early Cretaceous in Liaoning, China. Acta Geologica Sinica. 78(1), 1-7.
Zhou, Clarke and Zhang, 2008. Insight into diversity, body size and morphological evolution from the largest Early Cretaceous enantiornithine bird. Journal of Anatomy. 212, 565-577.

Hollanda Bell, Chiappe, Erickson, Suzuki, Watabe, Barsbold and Tsogtbaatar, 2009
H. luceria Bell, Chiappe, Erickson, Suzuki, Watabe, Barsbold and Tsogtbaatar, 2009
Late Campanian, Late Cretaceous
Barun Goyot Formation, Mongolia
Holotype- (MPC-b100/202) distal tibiotarsus, tarsometatarsus, proximal phalanx II-1, phalanx III-1, phalanx III-2, proximal phalanx III-3
Paratypes- ....(MPC-b100/203) distal femur
....(MPC-b100/204) proximal tibiotarsus
....(MPC-b100/205) proximal tibiotarsus
....(MPC-b100/206) fibula
....(MPC-b100/207) fibula
Comments- The type material was discovered in 1997 and first announced by Bell et al. (2008) as "a new taxon of primitive ornithuromorph bird." Bell et al. (2009) later described and named the material as a new taxon of basal ornithuromorph, either intermediate between Patagopteryx and songlingornithids or sister to Ornithurae sensu Chiappe. However, when included in a larger analysis with a greater variety of taxa, Hollanda emerges as a non-ornithuromorph ornithothoracine. Characters more primitive than ornithuromorphs include a lack of distal metatarsal fusion and proximal tarsometatarsal foramina absent, while characters shared with some enantiornithines include the posteriorly projected laterodistal femoral margin, and metatarsal IV reduced in width.
References- Bell, Chiappe, Suzuki and Watabe, 2008. Phylogenetic and morphometric analysis of a new ornithuromorph from the Barun Goyot Formation, Southern Mongolia. Abstracts of the 7th International Meeting of the Society of Avian Paleontology and Evolution.1.
Bell, Chiappe, Erickson, Suzuki, Watabe, Barsbold and Tsogtbaatar, 2009. Description and ecologic analysis of Hollanda luceria, a Late Cretaceous bird from the Gobi Desert (Mongolia). Cretaceous Research. doi:10.1016/j.cretres.2009.09.001

Lectavis Chiappe, 1993
L. bretincola Chiappe, 1993
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Holotype- (PVL-4021) (~575 mm) tibiotarsus (156 mm), incomplete tarsometatarsus
Diagnosis- (after Chiappe, 1993) tibiotarsus transversely wider than deep in proximal view; distal tibiotarsal condyles strongly projected anteriorly; slender tarsometatarsus (also in Hollanda and Neuquenornis); m. tibialis cranialis tubercle on metatarsal II circular; proximoplantar surface of metatarsal II forming prominent, thick edge (also in Hollanda); hypotarsus present and mostly developed on metatarsal II.
(proposed) plantar surface of tarsometatarsus excavated (also in Confuciusornis and Hollanda); m. tibialis cranialis tubercle on metatarsal II proximally placed (distance from proximal edge of tubercle to proximal edge of tarsometatarsus <60% transverse width of proximal tarsometatarsus).
Comments- Lectavis was originally identified as an enantiornithine (Walker, 1981; Chiappe, 1991) and was labeled Type-B by Chiappe (1992) before being named and described in 1993. It was illustrated in more detail by Chiappe and Walker (2002). Chiappe (1992) included Lectavis in a small phylogenetic analysis where it emerged as a non-avisaurid enantiornithine. Yet the three characters which placed it in Enantiornithes are now known in more basal taxa as well- plantar surface of tarsometatarsus excavated (Confuciusornis, Patagopteryx); m. tibialis cranialis tubercle on metatarsal II (Confuciusornis, PKUP 1069 and many other ornithuromorphs); metatarsal IV reduced in width (Zhongjianornis). Kurochkin (1996) included Lectavis in his Alexornithiformes incertae sedis based on its enlarged medial tibiotarsal condyle, m. tibialis cranialis tubercle on metatarsal II, and tarsometatarsal trochlea which differ in size. Yet Kurochkin's taxonomic scheme is flawed, as his euornithiforms Boluochia, Sinornis and Concornis have enlarged medial condyles as well, none of his euornithiforms are known to lack the metatarsal II tubercle, and his euornithiforms Iberomesornis, Boluochia, Sinornis and Concornis have enlarged metatarsal II trochlea. When included in a larger analysis, Lectavis has an uncertain position within Ornithothoraces but is not an ornithuromorph. It is likely to be an enantiornithine since all other bird remains at El Brete belong to that clade. Walker et al. (2007) incorrectly (mistakenly) assigned the holotype to Avisaurus.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Chiappe, 1991. Cretaceous birds of Latin-America. Cretaceous Research. 12, 55-63.
Chiappe, 1992. Enantiornithine (Aves) tarsometatarsi and the avian affinities of the Late Cretaceous Avisauridae. Journal of Vertebrate Paleontology. 12(3), 344-350.
Chiappe, 1993. Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates. 3083, 39 pp.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

Lenesornis Kurochkin, 1996
L. maltshevskyi (Nessov, 1986) Kurochkin, 1996
= Ichthyornis maltshevskyi Nessov, 1986
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 3434) (~330 mm) anterior synsacrum (~39 mm)
Comments- Kurochkin (1996) removed maltshevskyi from Ichthyornis and placed it in a new genus, which seems correct as Lenesornis differs in having broader anterior sacral centra which are ventrally grooved, a lower anterior articular surface, and a fourth sacral transverse process which is not short and dorsally directed. The latter character excludes it from Carinatae sensu Cracraft. Kurochkin noted Lenesornis is very similar to Gobipteryx, only differing in being less concave ventrally and having a broader anterior articular surface (height 73% of width instead of ~82%). Gargantuavis shares broad and low centra with a ventral groove and transverse processes which are similar where known, but differs in that it is very decurved anteriorly, lacks pleurocoels, has a smaller neural canal, and has a ventral keel on the first several vertebrae. Noguerornis differs in having amphiplatyan centra, while Iberomesornis has broader anterior sacral centra with a ventral median prominence. Hebeiornis' sacrum is poorly preserved, but shares the ventral groove with Gobipteryx, Pengornis, Lecho enantiornithine sacrum PVL-4045-2 and Lenesornis. The sacra of Zhyraornis and the Lecho enantiornithine PVL-4041-4 differ in having narrower anterior sacral centra without ventral grooves. Patagopteryx is similar in having a ventral sulcus, broad anterior surface and slight ventral concavity, though the centra appear broader compared to their length. Archaeorhynchus and Apsaravis also have broadly similar sacra in relative centrum width and at least Archaeorhynchus seems to have a ventral sulcus, though further details in either genus are unknown. Hesperornithines and neornithines differ in having a heterocoelous anterior articulation, while hesperornithines also differ in being non-pneumatic. Both Gansus and Guildavis have narrower centra without a ventral sulcus. Confuciusornis lacks a ventral sulcus anteriorly, though confuciusornithids do share a relatively broad sacrum with concave anterior articulation with Lenesornis. The third sacral rib is larger than in Sapeornis or Shenzhouraptor, though sacra of those taxa are only available in dorsal view, limiting comparisons. Non-ornithurines (sensu Gauthier) have less extensively fused sacra, especially at such small sizes. An exception is Avimimus, which is similar in having a lateral fossa in the first centrum and a ventral sulcus starting on the second centrum.
In conclusion, Lenesornis is most similar to some enantiornithines and basal ornithuromorphs, but is not an ornithurine sensu Chiappe (within the Hesperornis + Passer clade), and is probably an ornithurine sensu Gauthier (closer to Passer than to Archaeopteryx). However, comparisons with non-ornithothoracine birds are limited and the possibility Lenesornis is a very small and highly fused non-bird maniraptoriform like Avimimus cannot be excluded. Though it is distinguishable from other well described theropod sacra, most are too poorly preserved or described.
References- Nessov, 1986. The first record of the Late Cretaceous bird Ichthyornis in the Old World and some other bird bones from the Cretaceous and Paleogene of Soviet Middle Asia. Proc. Zool. Inst. USSR Acad. Sci.. 147, 31-38.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.

Platanavis Nessov, 1992
P. nana Nessov, 1992
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4601) (~150 mm) mid synsacrum (~18 mm)
Diagnosis- sacral pleurocoels present in midsacral vertebrae; sacral pleurocoels directed strongly ventrally; sacral pleurocoels very dorsoventrally compressed; extremely deep median ventral sulcus on mid sacrum (also in Gobipteryx).
Comments- Nessov (1992) included two additional characters in his diagnosis, but dorsoventrally compressed sacral centra are common in birds as are large neural canals.
Mourer-Chauvire (1989) first announced the discovery of this specimen in 1989 as "part of the strange flat sacrum of a small new bird." This taxon is based only on the mid portion of a synsacrum, containing two complete and two partial vertebrae. It was small, as the complete vertebrae are 2.9 and 2.5 mm long each. The vertebrae are dorsoventrally compressed (~64% as tall as wide) and elongate (1.18-1.4 times longer than maximum height). The preserved sequence is only very slightly concave ventrally, and each centrum has a straight ventral margin. The ventral surface features a narrow median sulcus, giving the appearance to paired ridges. There is a low and deep pleurocoel in each complete centrum which opens lateroventrally due to the especially broad dorsal area. The neural canal is very wide, at least as broad as the centra.
Both Nessov (1992) and Kurochkin (2000) have assigned it to Aves incertae sedis without comment. Indeed, the fused sacral vertebrae are too small to derive from adult non-avialan theropods. Even tiny Caenagnathasia and Ceratonykus would have had sacra three times larger, while Microraptor and Jinfengopteryx were twice as large. The large neural canal, dorsoventral compression and ventral groove are common in maniraptoriforms, including many basal birds. Unfortunately, most Mesozoic birds have poorly preserved sacra, and are often undescribed or only visible in dorsal view. Those of Confuciusornis are similar in having lateral fossae and a ventral groove, but the fossae are limited anteriorly while the groove is limited posteriorly. Zhyraornis' sacrum is more concave ventrally, has narrower centra and lacks a groove. It does have pleurocoels anteriorly, but these differ in being laterally directed. The Lecho Formation enantiornithine PVL-4041-4 and Guildavis are also more slender ventrally with no groove, and if they have pleurocoels, they are not directed lateroventrally. Apatornis' sacrum is narrower, especially anteriorly, and lacks pleurocoels. Gansus' sacrum is narrower and not grooved ventrally though it does seem to have somewhat ventrally angled central fossae on the anterior centra. Ichthyornis' sacrum has anterior centra which are too narrow, without a ventral groove, and only the first sacral has a slight central fossa, which is directed laterally. The posterior centra are broader with a slight ventral groove, but lack pleurocoels. Apsaravis has a broad sacrum, but lacks a ventral groove and pleurocoels. Gargantuavis has a broad sacrum with a ventral keel on the posterior half, but lacks pleurocoels. Gobipteryx's and Patagopteryx's sacra are similarly low and broad ventrally with a median groove, but they don't seem to have pleurocoels. Lenesornis' sacrum is similar in being broad and only slightly concave ventrally with a ventral sulcus, but the pleurocoels are limited anteriorly and laterally directed. The ventral grooves of Gargantuavis, Lenesornis and Patagopteryx seem far more shallow than that of Platanavis, while Gobipteryx's is comparably deep. Thus the closest similarity is with various ornithothoracines, though its relationships cannot be determined further given the fragmentary material and lack of many comparable taxa. It may end up being synonymous with one of the Bissekty's numerous enantiornithines, such as the comparably sized Explorornis nessovi or Incolornis silvae.
References- Mourer-Chauvire, 1989. Society of Avian Paleontology and Evolution Information Newsletter. 3.
Nessov, 1992. Review of localities and remains of Mesozoic and Paleogene birds of the USSR and the description of new findings. Russkii Ornitologicheskii Zhurnal. 1(1), 7-50.
Kurochkin, 2000. Mesozoic birds of Mongolia and the former USSR. in Benton, Shishkin, Unwin and Kurochkin, eds. The Age of Dinosaurs in Russia and Mongolia. 533-559.

unnamed probable ornithothoracine (Nessov, 1984)
Early Cenomanian, Late Cretaceous
Khodzhakul Formation, Uzbekistan
Material- (TsNIGRI 52/11915) dorsal vertebra (9 mm) (Nessov, 1984)
? fragments (Nessov, 1992)
Comments- Discovered in 1975, Nessov (1984) noted this specimen was amphicoelous with a shallower lateral fossa than "Zhyraornis kashkarovi" TsNIGRI 43/11915. It is from an avebrevicaudan due to its large lateral central fossae, probably an ornithothoracine based on its age. Nessov (1992) noted unidentified fragments of small bird bones were found in the same locality.
References- Nessov, 1984. [Upper Cretaceous pterosaurs and birds from Central Asia] Paleontologicheskii Zhurnal. 1, 47-57.
Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

unnamed possible ornithothoracine (Nessov, 1986)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 3434f) braincase fragment, atlas, axis
Comments- This specimen was listed as Aves indet. by Nessov (1992), but could conceivably derive from a small non-avian coelurosaur as well.
References- Nessov, 1986. The first record of the Late Cretaceous bird Ichthyornis in the Old World and some other bird bones from the Cretaceous and Paleogene of Soviet Middle Asia. Proceedings of the Zoological Institute, Leningrad. 147, 31-38.
Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

unnamed probable ornithothoracine (Nessov, 1984)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (TsNIGRI 52/11915) pedal phalanx (21.3 mm)
Comments- This is far more elongate than any non-bird theropod, so may belong to an ornithuromorph or specialized enantiornithine.
Reference- Nessov, 1984. [Upper Cretaceous pterosaurs and birds from Central Asia] Paleontologicheskii Zhurnal. 1, 47-57.

undescribed possible ornithothoracine (Mourer-Chauvire, 1989)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- posterior synsacrum
Comments- Mourer-Chauvire (1989) noted an ichthyornithiform sacrum, and Nessov (1992) mentioned a posterior synsacrum discovered in 1989, "possibly with affinities to ichthyornithiformes." Besides the size, said to be similar to a recent coromorant, no further details are known. It may indeed by an ichthyornithine, but could also be a more basal ornithuromorph, an enantiornithine, or even a non-bird theropod.
Reference- Mourer-Chauvire, 1989. Society of Avian Paleontology and Evolution Information Newsletter. 3.
Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

unnamed possible ornithothoracine (Nessov, 1992)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4610) tooth (3.2 mm)
Comments- Nessov (1992a) noted teeth of small birds discovered in 1989, one of which was later illustrated by him (1992b) as possibly being ichthyornithiform. Yet the tooth differs from Ichthyornis is being straight, more slender, and having a basally expanded crown, and being uncompressed labiolingually. Those features are more closely approached by Dinosaur Park Formation teeth like RTMP 96.62.51, but it is more compressed as well. Perhaps it is an anterior tooth. If it is indeed a bird and not a mammal or crocodilian, it seems distinct from other well described examples.
References- Nessov, 1992a. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.
Nessov, 1992b. Review of localities and remains of Mesozoic and Paleogene birds of the USSR and the description of new findings. Russkii Ornitologicheskii Zhurnal. 1(1), 7-50.

unnamed probable ornithothoracine (Nessov, 1992)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4608) partial dentary
Comments- Nessov (1992a) noted a possibly ichthyornithiform mandible discovered in 1989, which seems to be the partial dentary ascribed by him later (1992b) to Ichthyornithiformes. The preserved portion differs from Ichthyornis in being more slender and upcurved. It is not troodontid because it lacks a lateral groove, and differs from that family, Dromaeosauridae and Alvarezsauridae in having distinct alveoli. It is here placed in Ornithothoraces incertae sedis (but is not part of Aves sensu lato), as no more basal toothed avialans are known to exist by the Turonian.
References- Nessov, 1992a. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.
Nessov, 1992b. Review of localities and remains of Mesozoic and Paleogene birds of the USSR and the description of new findings. Russkii Ornitologicheskii Zhurnal. 1(1), 7-50.

unnamed ornithothoracine (Nessov, 1992)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4621) posterior mandible
Comments- Nessov (1992a) noted a posterior bird mandible discovered in 1989, which seems to be the one later figured by him as PO 4621 (Nessov, 1992b). It seems to be ornithothoracine based on the concave dorsal surangular edge, but further comparison is necessary to determine its precise relationships.
References- Nessov, 1992a. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.
Nessov, 1992b. Review of localities and remains of Mesozoic and Paleogene birds of the USSR and the description of new findings. Russkii Ornitologicheskii Zhurnal. 1(1), 7-50.

unnamed ornithothoracine (Nessov, 1992)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4613) distal humerus
Comments- Nessov (1992a) noted "part of a humerus of a medium-sized bird with strange morphology (possibly a new group of Aves" discovered in 1989. This is probably the distal humerus PO 4607 later (1992b) figured by him as possibly enantiornithine. Indeed, the humerus resembles enantiornithines in having a strongly distally projected ventral condyle and transversely oriented dorsal condyle. Yet these are present in Apsaravis as well, leaving the specimen referred to Ornithothoraces incertae sedis.
References- Nessov, 1992a. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.
Nessov, 1992b. Review of localities and remains of Mesozoic and Paleogene birds of the USSR and the description of new findings. Russkii Ornitologicheskii Zhurnal. 1(1), 7-50.

unnamed ornithothoracine (Nessov, 1992)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 3434c) distal humerus
Comments- Nessov (1992) illustrated a distal humerus he questionably referred to Alexornithiformes. The humerus does resemble enantiornithines in having a strongly distally projected ventral condyle, but this is seen in Apsaravis as well, leaving the specimen referred to Ornithothoraces incertae sedis.
References- Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

undescribed possible Ornithothoraces (Nessov, 1992)
Early Santonian, Late Cretaceous
Yalovach Formation, Tajikistan
Material- fragments
Comments- Nessov (1992) notes rare fragments of birds are present in this locality (spelled Jalovatsh in his paper).
Reference- Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

undescribed probable ornithothoracine (Nessov, 1992)
Santonian, Late Cretaceous
Bostobe Formation, Kazakhstan
Material- (PO 3475) pedal ungual (6.6 mm)
Comments- This is probably an ornithothoracine based on the large flexor tubercle and age, but further determination is difficult.
Reference- Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

undescribed possible Ornithothoraces (Nessov, 1992)
Late Maastrichtian, Late Cretaceous
Kakanaut Formation, Russia
Comments- Nessov (1992) merely says there are "bones of presumably medium-sized birds" in this locality.
Reference- Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.

unnamed ornithothoracine (Nessov and Panteleev, 1993)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4821) partial coracoid
Comments- This was referred to Enantiornithes by Nessov and Panteleev (1993), then later specifically to Alexornithiformes by Panteleev (1998). While the deep dorsal fossa is found in enantiornithines, it is also present in Apsaravis, limiting identication of this element to Ornithothoraces incertae sedis.
References- Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk. 35, 3-15.

undescribed probable Ornithothoraces (MOR online)
Late Campanian, Late Cretaceous
Judith River Group, Montana, US
Material- (MOR 023) vertebra
?(MOR 1044) partial skeleton
Comments- MOR 023 was listed as "bird", while MOR 1044 was listed as "theropod, bird?".

undescribed probable Ornithothoraces (MOR online)
Late Maastrichtian, Late Cretaceous
Hell Creek Formation, Montana, US
Material- (MOR 978) distal humerus, femur
(MOR 1086) distal humerus
(MOR 2716) distal metatarsal
(MOR 2917) distal femur
(MOR 2918) coracoid
Comments- These were listed as bird remains on MOR's online specimen catalog, so are probably ornithothoracines based on their age.

undescribed possible Ornithothoraces (MOR online)
Late Cretaceous
MV-150, Montana, US
Material- (MOR 1461)
Comments- This was listed as a possible bird on MOR's online specimen catalog.

Enantiornithes Walker, 1981
Definition- (Enantiornis leali <- Passer domesticus) (modified from Longrich, 2009)
Other definitions- (Sinornis santensis <- Passer domesticus) (Sereno, in press; modified from Sereno, 1998)
= Euornithiformes Kurochkin, 1996
= Enantiornithes sensu Sereno, 1998
Definition- (Sinornis santensis <- Passer domesticus) (modified)
= Enantiornithomorpha Chiappe, Ji, Ji and Norell, 1999
Diagnosis- laterally compressed proximal coracoid (also in many Neognathae; absent in Catenoleimus, Explorornis nessovi and Elsornis); m. tibialis cranialis tubercle on tarsometatarsus confined to metatarsal II (also in Velociraptor and PKUP 1069; absent in Vorona, Rapaxavis and Yungavolucris); metatarsal II trochlea transversely expanded (also in Falcarius, some paravians and Zhongjianornis; absent in Alethoalaornis, Longipterygidae and Liaoningornithidae); metatarsal IV reduced in width (also in Archaeopteryx and Zhongjianornis; absent in Iberomesornis, Shanweiniao and Liaoningornithidae).

Abavornis Panteleev, 1998
A. bonaparti Panteleev, 1998
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (TsNIGRI 56/11915) (~280 mm) coracoid shaft (~32 mm)
Diagnosis- (after Pantellev, 1998) significant medial expansion of distal coracoid; deep dorsal coracoid fossa (also in Neuquenornis and Enantiornis); longitudinal groove along ventromedial edge of shaft.
(proposed) laterodistal edge angles medially.
Comments- Originally identified as Aves by Nessov and Borkin (1983) and Nessov (1984), then as Enantiornithes by Nessov and Panteleev (1993). Elzanowski (1995) believed the specimen was nearly identical to "Gobipipus" (which he referred to juvenile Gobipteryx) and referred it to Gobipterygidae and perhaps Gobipteryx itself. However, it differs from "Gobipipus" in having the lateral edge angle distomedially, a longer shaft between the dorsal fossa and head, the supracoracoid foramen placed completely proximal to the dorsal fossa, and a rounded proximal edge of the dorsal fossa. In addition to these characters, it differs from adult Gobipteryx in having a wider shaft, deeper dorsal fossa, more distomedial expansion and a ventromedial groove. Kurochkin (1996) referred the coracoid to Enantiornithidae indet., based on the deep and proximally extensive dorsal fossa and convex lateral margin. The former is also found in his alexornithid Neuquenornis however, while the latter is found in his concornithids Concornis and Sinornis. Panteleev (1998) described the specimen as the holotype of his new genus Abavornis, which he placed in the Alexornithidae and Alexornithiformes without comment.
References- Nessov and Borkin, 1983. [New Records of Bird Bones from Cretaceous of Mongolia and Middle Asia]. Trudy Zoologicheskogo Instituta Akademii Nauk SSSR. 116, 108-110.
Nessov, 1984. [Upper Cretaceous pterosaurs and birds from Central Asia] Paleontologicheskii Zhurnal. 1, 47-57.
Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Elzanowski, 1995. Cretaceous birds and avian phylogeny. Cour. Forschungsinst. Senckenb. 181, 37-53.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk. 35, 3-15.
A? sp. nov. (Panteleev, 1998)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4605) (~180 mm) coracoid shaft (~21 mm)
Comments- Originally identified as Aves by Nessov (1992), then Enantiornithes by Nessov (1997). This is based off the distal part of a coracoid, missing the distolateral corner. It closely resembles Avabornis bonaparti, but the lateral edge is straight, not angled inward distally. Perhaps the edge of A. bonaparti is broken.
References- Nessov, 1992. [Record of the Localities of Mesozoic and Paleogene with Avian Remains in the USSR, and the description of New Findings]. Russian Journal of Ornithology. 1, 7-50.
Nessov, 1997. [Cretaceous nonmarine vertebrates of northern Eurasia]. Saint Petersburg, Institute of Earth Crust. 1-218.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.

Catenoleimus Panteleev, 1998
C. anachoretus Panteleev, 1998
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4606) (~220 mm) coracoid shaft (~25 mm)
Comments- Originally identified as Enantiornithes in Nessov (1992).
Reference- Nessov, 1992. [Record of the Localities of Mesozoic and Paleogene with Avian Remains in the USSR, and the description of New Findings]. Russian Journal of Ornithology. 1, 7-50.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.

Cuspirostrisornithidae Hou, 1997
Cuspirostrisornis Hou, 1997
C. houi Hou, 1997
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V10897) (~140 mm) incomplete skull (~27 mm), dentaries, four or five cervical vertebrae, five or six dorsal vertebrae, sacrum, several caudal vertebrae, pygostyle, partial coracoid, sternum (~23 mm), humeri (29 mm), radii (29.5 mm), ulnae (32 mm), carpometacarpus (14 mm), manual ungual, ilium, pubis, ischium, femora (27.3 mm), tibiotarsi (32.5 mm), fibulae (~8.5 mm), tarsometatarsi (19 mm), pedal phalanges, pedal ungual I (8 mm), pedal ungual II (8 mm), pedal ungual III (9 mm), pedal ungual IV (6 mm)
Diagnosis- distal portion of posterolateral sternal processes not fused to sternum.
Reference- Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.

Enantiophoenix Cau and Arduini, 2008
E. electrophyla Cau and Arduini, 2008
Middle Cenomanian, Late Cretaceous
Ouadi al Gabour, Lebanon
Holotype- (MSNM V3882) rib fragments, synsacrum, scapula (21.3 mm), coracoids (one partial; 19.4 mm), partial furcula, partial sternum, ilial fragment, incomplete pubis, ischial fragments, incomplete tarsometatarsi (~28 mm), four pedal phalanges, four pedal unguals, long bone shafts, two distal phalanges, two unguals, feathers
Comments- This specimen was briefly described as an enantiornithine but unnamed by Dalla Vecchia and Chiappe (2002), then described in detail and named by Cau and Arduini (2008). Cau and Arduini assigned Enantiophoenix to the Avisauridae based on their phylogenetic analysis.
References- Dalla Vecchia and Chiappe, 2002. First avian skeleton from the Mesozoic of Northern Gondwana. Journal of Vertebrate Paleontology. 22(4), 856-860.
Cau and Arduini, 2008. Enantiophoenix electrophyla gen. et sp. nov. (Aves, Enantiornithes) from the Upper Cretaceous (Cenomanian) of Lebanon and its phylogenetic relationships. Atti Soc. it. Sci. nat. Museo civ. Stor. nat. Milano. 149(II), 293-324.

"Enantiornis" walkeri Nessov and Panteleev, 1993
= Explorornis walkeri (Nessov and Panteleev, 1993) Panteleev, 1998
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4825) (~300 mm) proximal coracoid (~35 mm)
Diagnosis- (proposed) acrocoracoid process dorsoventrally deep (>50% as deep at level of junction between scapular facet and acrocoracoid as the coracoid head is long); coracoid lateral convexity begins on shaft proximal to dorsal fossa.
Other diagnoses- Nessov and Panteleev (1993) distinguished walkeri from Enantiornis leali based on several characters. The coracoid process is not narrower however. The acrocoracoid process is not actually shorter than in Enantiornis, but appears so due to its depth. The proximal shaft is transversely wider, but this is plesiomorphic. The elongate supracoracoid foramen seems to be the medial exit, which is also elongate in Enantiornis.
Kurochkin (2000) listed two features in his diagnosis to separate walkeri from leali. The coracoid process is even more stout in Explorornis, and equally so in Incolornis, Neuquenornis and Catenoleimus. The proximal shaft is more gracile dorsoventrally, but this is also true of Gurilynia, Gobipteryx and Explorornis.
Comments- This specimen was discovered in 1991 and named "Enantiornis" walkeri by Nessov and Panteleev (1993). While the quotation marks suggest they did not believe the species to actually be Enantiornis, they did place it within the Enantiornithiformes. Kurochkin (1996) removed the quotation marks, as he believed it was referrable to Enantiornis based on the obtuse acrocoracoid tip, stout coracoid process and proximally (dorsoventrally?) thick shaft. However, the acrocoracoid tip is no more obtuse than Explorornis, Incolornis martini and Alexornis, the coracoid process is less stout in Enantiornis than in Explorornis, Incolornis, Catenoleimus, Otogornis or Neuquenornis, and the shaft isn't thick as in Enantiornis and is much thinner than in Incolornis. Kurochkin (2000) later kept the species in Enantiornis and added a couple coracoid features to his diagnosis of the genus- short coracoid shaft; stout acrocoracoid process. The former is plesiomorphic, while the latter is also present in Otogornis and Incolornis. Panteleev (1998) transferred walkeri to his new genus Explorornis (within Alexornithidae and Alexornithiformes) without justification, though it does share that genus' primitive dorsoventrally compressed coracoid shaft and shallow dorsal fossa. Yet it lacks the apomorphic dorsolateral ridge of Explorornis. walkeri does not seem to be definitively referrable to either genus.
References- Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.
Kurochkin, 2000. Mesozoic birds of Mongolia and the former USSR. in Benton, Shishkin, Unwin and Kurochkin, eds. The Age of Dinosaurs in Russia and Mongolia. 533-559.
E? sp. (Panteleev, 1998)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4817) proximal coracoid (~28 mm)
Comments- This coracoid is not figured, but Panteleev says it resembles walkeri more than E. nessovi or the other Explorornis species. Its true relationships remain unknown.
Reference- Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.

"Holbotia" Kurochkin, 1991
= "Kholbotiaka" Kurochkin, 1994
"H. ponomarenkoi" Kurochkin, 1991
Hauterivian-Barremian, Early Cretaceous
Andaikhudag Formation, Mongolia
Material- skull, pectoral girdle, hindlimb, feather impressions
Comments- This name originally appeared as a label on a fossil photographed in Kurochkin, 1991. The caption indicates it was supposed to belong to a pterosaur, and the name was attributed to Kurochkin, 1982. The lack of description makes this a nomen nudum. Unwin (1993) reffered the remains to the Ambiortidae and possibly to Ambiortus. However, Kurochkin later (1994, 1995, 2000) refers the specimen to the Enantiornithes. This seems true, given the elongate hypocleidium and V-shaped fucula. These features also eliminate the possibility this is synonymous with or closely related to Ambiortus. However, Kurochkin's (2000) assignment of this specimen to his Euornithiformes within Enantiornithines is unjustified, as is the reality of Euornithiformes itself. Kurochkin's later spelling "Kholbotiaka" in an abstract is a direct translation from Cyrillic, and not new proposed name as such.
References- Kurochkin, 1991. Protoavis, Ambiortus, and other palaeornithological rarities. Priroda. 1991(12), 43-53 [In Russian].
Unwin, 1993. Chapter 40. Aves. In Benton (Ed.). The Fossil Record 2, p.717-738. Chapman and Hall, NY.
Kurochkin, 1994. Synopsis and Evolution of Mesozoic Birds. Journal Für Ornithologie. 135.
Kurochkin, 1995. Synopsis of Mesozoic Birds and Early Evolution of Class Aves. Archaeopteryx. 13, 47-66.
Kurochkin, 2000. Mesozoic birds of Mongolia and the former USSR. in Benton, Shishkin, Unwin and Kurochkin (eds.). The Age of Dinosaurs in Russia and Mongolia. 533-559.

Iberomesornithiformes Sanz and Bonaparte, 1992
Iberomesornithidae Sanz and Bonaparte, 1992
Iberomesornis Sanz and Bonaparte, 1992
I. romerali Sanz and Bonaparte, 1992
Late Barremian, Early Cretaceous
Calizas de La Huerguina Formation, Spain
Holotype- (LH-22) (87 mm) fragment of sixth cervical vertebra, seventh cervical vertebra (2.3 mm), eighth cervical vertebra (2.2 mm), ninth cervical vertebra (1.9 mm), tenth cervical vertebra (1.8 mm), first dorsal vertebra (1.7 mm), second dorsal vertebra (1.7 mm), third dorsal vertebra (1.7 mm), fourth dorsal vertebra (1.7 mm), fifth dorsal vertebra (1.7 mm), sixth dorsal vertebra (1.7 mm), seventh dorsal vertebra (1.7 mm), eighth dorsal vertebra (1.8 mm), ninth dorsal vertebra (1.8 mm), tenth dorsal vertebra (1.7 mm), eleventh dorsal vertebra (1.7 mm), thirteen dorsal ribs, dorsal rib fragments, first sacral vertebra (1.4 mm), second sacral vertebra (1.4 mm), third sacral vertebra, fourth sacral vertebra (~1.3 mm), fifth sacral vertebra (~1.3 mm), sixth sacral vertebra (1.2 mm), seventh sacral vertebra (1 mm), eighth sacral vertebra (.9 mm), first caudal vertebra (.9 mm), second caudal vertebra (.9 mm), third caudal vertebra (.9 mm), fourth caudal vertebra (.9 mm), fifth caudal vertebra (.9 mm), sixth caudal vertebra (.8 mm), six chevrons, pygostyle (9.2 mm), partial scapula (10.1 mm), coracoids (9.9 mm), furcula, partial sternum, eight sternal ribs, incomplete humerus (~17.6 mm), radius (18.2 mm), incomplete ulna (~19.2 mm), partial ilia (10.3 mm), partial pubes, ischia, incomplete femora (16.4 mm), tibiotarsi (20 mm), metatarsal I (2.4 mm), phalanx I-1 (2.9 mm), pedal ungual I (2.5 mm), metatarsal II (11.2 mm), phalanx II-1 (2.3 mm), phalanx II-2 (3.5 mm), pedal ungual II (2.2 mm), metatarsal III (11.8 mm), phalanx III-1 (3.2 mm), phalanx III-2 (2.8 mm), phalanx III-3 (3.4 mm), pedal ungual III (2.3 mm), metatarsal IV (11.5 mm), phalanx IV-1 (1.9 mm), phalanx IV-2 (1.6 mm), phalanx IV-3 (1.7 mm), phalanx IV-4 (2.4 mm), pedal ungual IV (1.8 mm)
Referred- ?(LH-8200) metatarsal I, pedal phalanx I-1, pedal ungual I, tarsometatarsus (14 mm), pedal phalanx II-1, pedal phalanx II-2, pedal ungual II, pedal phalanx III-1, pedal phalanx III-2, pedal phalanx III-3, pedal ungual III, pedal phalanx IV-1, pedal phalanx IV-2, pedal phalanx IV-3, pedal phalanx IV-4, pedal ungual IV (Sanz and Buscalioni, 1994)
Diagnosis- pubic peduncle of ilium directed anteroventrally.
References- Sanz and Bonaparte, 1992. A new order of birds (Class Aves) from the Lower Cretaceous of Spain. pp 38-49. in Campbell (ed.). Papers in Avian Paleontology. Honoring Pierce Brodkorb. Science Series 36, Natural History Museum of Los Angeles County, Los Angeles.
Sanz and Buscalioni, 1994. An isolated bird foot from the Barremian (Lower Cretaceous) of Las Hoyas (Cuenca, Spain). Géobios, Mémoire Spéciale. 16:213-217.
Sereno, 2000. Iberomesornis romerali (Ornithothoraces, Aves) re-evaluated as an enantiornithine bird. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 215, 365-395.
Sanz, Pérez-Moreno, Chiappe and Buscalioni, 2002. The Birds from the Lower Cretaceous of Las Hoyas (Privince of Cuenca, Spain). pp 209-229. in Chiappe and Witmer (eds.). Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

"Ichthyornis" minusculus Nessov, 1990
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistanan
Holotype- (PO 3941) (~205 mm) dorsal vertebra (4 mm)
Comments- Mourer-Chauvire (1989) mentioned this as a "vertebra of an Ichthyornithiform the size of a thrush." This specimen can be assigned to Enantiornithes based on its centrally located parapophysis.
References- Mourer-Chauvire, 1989. Society of Avian Paleontology and Evolution Information Newsletter. 3.
Nessov, 1990. Small ichthyornithiform bird and other bird remains from Bissekty Formation (Upper Cretaceous) of central Kyzylkum Desert. Proceedings of the Zoological Institute, Leningrad. 210, 59-62 (in Russian).
Kurochkin, 1996. A new Enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue: 50pp.

Incolornis Panteleev, 1998
Diagnosis- (proposed) very deep coracoid shaft (>40% of proximodistal head length); proximodorsal bump located on shaft just distal to scapular facet.
Other diagnoses- Panteleev (1998) listed three diagnostic characters for Incolornis. Of these, the ventral longitudinal ridge on the coracoid shaft is also present in Iberomesornis, Enantiornis and Gobipteryx. The narrow coracoid tubercle is found in a wide range of taxa (e.g. Catenoleimus, Elsornis, Gurilynia, Enantiornis, Eocathayornis, Sinornis). Finally, the supracoracoid foramen has its proximal exit on the middle of the medial side of the shaft in Enantiornis, Otogornis and Neuquenornis as well.
Reference- Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.
I. silvae Panteleev, 1998
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4604) (~135 mm) proximal coracoid (~15 mm)
Diagnosis- (after Panteleev, 1998) smaller than I. martini.
(proposed) proximodorsal coracoid bump placed further distally than in I. martini.
Comments- This was discovered in 1989 and originally identified as Enantiornithes(?) by Nessov and Panteleev (1993) and Nessov (1997). Panteleev (1998) made it the type species of his new genus Incolornis
References- Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Nessov, 1997. [Cretaceous nonmarine vertebrates of northern Eurasia]. Saint Petersburg, Institute of Earth Crust. 1-218.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35, 3-15.
I. martini (Nessov and Panteleev, 1993) Panteleev, 1998
= Enantiornis martini Nessov and Panteleev, 1993
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4609) (~220 mm) proximal coracoid (~25 mm)
Diagnosis- (after Panteleev, 1998) larger than I. silvae.
(proposed) proximodorsal coracoid bump placed further proximally than in I. silvae.
Other diagnoses- Kurochkin (1996) listed the narrow coracoid tubercle as a diagnostic feature, but as noted in the genus diagnosis, this is widespread in enantiornithines. He also listed the stout shaft, which is covered in the genus diagnosis above.
Panteleev (1998) also distinguishes I. martini from I. silvae based on the supposedly less transversely flattened coracoid shaft, but this seems untrue as I. martini has a width/depth ratio of 69% while I. silvae's is 74%. His final character is the larger groove between the glenoid and acrocoracoid in I. martini, but this could be due to erosion in I. silvae's holotype.
Comments- This was discovered in 1989 and originally figured as a scapula of Enantiornithidae indet. by Nessov (1992). It was later described as "Enantiornis" martini by Nessov and Panteleev (1993), which may indicate they did not feel it belonged in that genus. Kurochkin (1996) believed it was Enantiornis based on the obtuse acrocoracoid tip and stout coracoid process. However, the acrocoracoid tip is no more obtuse than Explorornis, walkeri, and Alexornis, and the coracoid process is less stout in Enantiornis than in Explorornis, Catenoleimus, Otogornis or Neuquenornis. Kurochkin (2000) later kept the species in Enantiornis and added a couple coracoid features to his diagnosis of the genus- short coracoid shaft; stout acrocoracoid process. The former is plesiomorphic, while the latter is also present in Otogornis and walkeri. Panteleev (1998) referred this species to his new genus Incolornis, based on I. silvae, which seems correct despite his listed diagnosis for the genus being problematic.
References- Nessov, 1992. [Record of the Localities of Mesozoic and Paleogene with Avian Remains in the USSR, and the description of New Findings]: Russian Journal of Ornithology. 1, 7-50.
Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35, 3-15.
Kurochkin, 2000. Mesozoic birds of Mongolia and the former USSR. in Benton, Shishkin, Unwin and Kurochkin, eds. The Age of Dinosaurs in Russia and Mongolia. 533-559.

Longchengornis Hou, 1997
L. sanyanensis Hou, 1997
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V10530) (~110 mm) frontals, parietals, axis (3 mm), postaxial cervical vertebrae, dorsal vertebrae, dorsal ribs, sacrum (14 mm), fifteen caudal vertebrae, scapula, coracoids (17 mm), furcula, sternum, humeri (32.5 mm), radius (29 mm), ulna, radiale, ulnare, metacarpal I, phalanx I-1, manual ungual I, carpometacarpus (15 mm), manual phalanx II-1, partial ilium (17 mm), pubis (~21 mm), ischium (~11 mm), femur (21.5 mm), tibiotarsi (~34 mm), fibula, pedal phalanx I-1 (5.5 mm), pedal ungual I (7 mm), tarsometatarsus (~21.5 mm), pedal phalanx II-1, pedal phalanx II-2, pedal ungual II (8 mm), pedal phalanx III-1, pedal phalanx III-2, pedal phalanx III-3, pedal ungual III, pedal phalanx IV-1, pedal phalanx IV-2, pedal phalanx IV-3, pedal phalanx IV-4, pedal ungual IV
Diagnosis- large foramen in proximal humerus.
Reference- Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.

unnamed Enantiornithes (Walker, 1981)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (MACN-S-02) (Chiappe, 1996)
(PVL-4021-2) fragmentary sternum (Chiappe and Calvo, 1994)
(PVL-4026) (Chiappe, 1996)
(PVL 4027) (Chiappe, 1996)
(PVL-4031) (Chiappe, 1996)
(PVL-4032) ulna, tibiotarsus (Chiappe, 1996)
(PVL-4032-3) incomplete pelvis (Walker, 1981)
(PVL-4034) coracoid (Chiappe and Walker, 2002)
(PVL-4036) femur (Chiappe and Calvo, 1994)
(PVL-4041-4) sacrum, ilium (Chippe and Walker, 2002)
(PVL-4042) ilium, ischium (Walker et al., 2007)
(PVL-4044) (Chiappe, 1996)
(PVL-4045-2) sacrum (Chiappe, 1996)
(PVL-4047) dorsal vertebrae (Chiappe and Calvo, 1994)
(PVL-4048) femur (Chiappe, 1996)
(PVL-4050) mid cervical (Chiappe, 1996)
(PVL-4056) (Chiappe, 1996)
(PVL-4057) mid cervical (Chiappe, 1996)
(PVL-4058) (Chiappe, 1996)
(PVL-4060) femur (Chiappe and Calvo, 1994)
(PVL-4180) (Chiappe, 1996)
(PVL-4267) (Chiappe, 1996)
(PVL-4269) (Chiappe, 1996)
(PVL-4271) (Chiappe, 1996)
(PVL-4273) proximal femur (~60 mm) (Chiappe and Calvo, 1994)
(PVL-4691) (Chiappe, 1996)
(PVL-4693) (Chiappe, 1996)
(PVL-4694) (Chiappe, 1996)
(PVL-4695) (Chiappe, 1996)
(PVL-4696) (Chiappe, 1996)
(PVL-4697) (Chiappe, 1996)
?(PVL-4698) posterior mandible (Chiappe, 1996)
(PVL-4703) (Chiappe, 1996)
Comments- A large amount of mostly disarticulated enantiornithine specimens have been found in the Lecho Formation. Most have not yet been described, and many have only appeared as specimen numbers in Chiappe (1996). Even fewer have been illustrated, most of which are given separate entries here as they can be referred to less inclusive clades within Enantiornithes (Euenantiornithes, Avisauridae, etc.). Five humeral morphologies are known from the site (including one named Enantiornis), and three tarsometatarsal morphologies (Lectavis, Yungavolucris and Soroavisaurus). These specimens probably belong to those taxa. Chiappe and Walker (2002) state that all of these elements have enantiornithine synapomorphies with the exception of PVL-4698, as they did not know of any mandibular characters which are diagnostic of Enantiornithes. Though several basal euornithines are now known to exhibit enantiornithine characters (e.g. Apsaravis), it's probable the Lecho specimens are all enantiornithines, as none have been shown to be euornithine or non-ornithothoracine.
PVL-4050 and 4057 are mid cervical vertebrae noted by Chiappe (1996) and Chiappe and Walker (2002) which are ornithurine (sensu Gauthier) due to their heterocoelous anterior surfaces, but unlike most euornithines (except Archaeorhynchus, Yixianornis, Gansus and Ichthyornis) in lacking heterocoelous posterior surfaces. Their centra are highly compressed tranversely, as in enantiornithines and Ichthyornis.
PVL-4021-2 is a sternum noted by Chiappe and Calvo (1994) as having deep posterior notches, implying the distal ends of the posterolateral processes are fused to it, an ornithothoracine character.
PVL-4034 is a coracoid mentioned by Chiappe and Walker (2002) which has a couple characters found in enantiornithines (deep fossa in dorsal surface; coracoid foramen passes through coracoid). However, both characters are also present in Apsaravis.
PVL-4032-3 is a pelvis missing most of the pubis and the distal ischium, illustrated by Walker (1981) and later Chiappe and Walker (2002). Walker et al. (2007) mentioned an ilium and ischium as PVL-4042, which may be this same specimen and was said to be consistant in size with Enantiornis. The complete pelvic fusion is more similar to euornithines than enantiornithines, though the elongate proximodorsal ischial process is only known in confuciusornithids and enantiornithines and the m. cuppedicus fossa is unlike euornithines. The low pointed postacetabular process is a symplesiomorphy only retained in Archaeorhynchus among euornthines, though found in most enantiornithines (except Gobipteryx).
PVL-4041-4 is a synsacrum and articulated ilia illustrated by Chiappe and Walker (2002). The ilia contact over the sacrum, which is otherwise only known in neognaths (Chiappe and Walker note it may be due to distortion). However, the ilium does not extend anterior to the sacral vertebrae, unlike Gansus and Aves. Furthermore, the postacetabular process is vertically oriented, unlike Carinatae sensu Chiappe. The presence of eight sacral vertebrae establishes the specimen as an enantiornithine as derived as Iberomesornis or an ornithothoracine.
PVL-4036, 4048, 4060 and 4273 are all femora attributible to Enantiornithes based on their hypertrophied posterior trochanters. The proximal end of PVL-4060 was illustrated schematically by Chiappe and Calvo (1994), while 4036 and 4048 were photographed by Chiappe (1996). PVL-4273 was illustrated by Chinsamy et al. (1995) and its histology was examined.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Chiappe and Calvo, 1994. Neuquenornis volans, a new Enantiornithes (Aves) from the Upper Cretaceous of Patagonia (Argentina). Journal of Vertebrate Paleontology. 14, 230–246.
Chinsamy, Chiappe and Dodson, 1995. Mesozoic avian bone microstructure: Physiological implications. Paleobiology. 21(4), 561-574.
Chiappe, 1996. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. Munchner Geowissenschaftliche Abhandlungen (A). 30, 203–244.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

unnamed probable enantiornithine (Nessov, 1988)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 3473) axis (13.5 mm)
Comments- Nessov (1988, 1992a) originally assigned this axis to Aves, then later (1992b) stated it was similar to Gaviidae. Kurochkin (1996) assigned it to Alexornithidae within Enantiornithines. This was based on several characters- general elongation; poorly developed prezgyapophyseal facets; lateral extensions of the prezgyapophyseal facets; broad neural arch; dorsally flat posterior neural arch that is projected posteriorly; low neural spine; shallow lateral central fossa. These were compared favorably to Gobipteryx (his Nanantius valifanovi) which he included in Alexornithidae, but it should be noted how few enantiornithine axes are known and described. The axis of Hebeiornis shares the poorly developed prezygapopgyses, lateral prezgyapophyseal extensions and broad neural arch, though it is less elongate and seemingly has a less posteriorly extensive neural arch. That of LP-4450-IEI has the broad neural arch and low neural spine, but is less elongate. Those of GMV-2158, Eocathayornis and Eoenantiornis are much shorter, but cannot be compared otherwise. Additionally, many of the characters have a broader distribution. Both Confuciusornis and Patagopteryx have axes with low neural spnes and shallow lateral fossae, for instance. It is tentatively retained here as an enantiornithine closer to Gobipteryx than the other taxa mentioned above based on elongation, but it should be compared to a wider range of coelurosaurs as well.
References- Nessov, 1988. [New Cretaceous and Paleogene birds of Soviet Middle Asia and Kazakhstan and their environments] Trudy Zoologicheskogo Instituta. 182, 31-38.
Nessov, 1992a. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.
Nessov, 1992b. Review of localities and remains of Mesozoic and Paleogene birds of the USSR and the description of new findings. Russkii Ornitologicheskii Zhurnal. 1(1), 7-50.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.

undescribed enantiornithine (Hutchison, 1993)
Late Campanian, Late Cretaceous
Kaiparowitz Formation, Utah, US
Material- (UCMP 139500) incomplete skeleton including pygostyle, coracoid, ulna, femur and pes
Comments- Hutchinson (2001) illustrates the proximal femur.
References- Hutchison, 1993. Avisaurus: a "dinosaur" grows wings. Abstract. Journal of Veterbrate Paleontology. 13(3), 43A.
Stidham, 1999. North American avisaurids (Aves: Enantiornithes): New data on morphology and phylogeny. VII International Symposium on Mesozoic Terrestrial Ecosystems, abstracts.
Hutchinson, 2001. The evolution of femoral osteology and soft tissues on the line to extant birds (Neornithes). Zool. J. Linn. Soc. 131, 169–197.
Stidham and Hutchison, 2001. The North American avisaurids (Aves: Enantiornithes): New data on biostratigraphy and biogeography. Asociación Paleontológica Argentina, Publicación Especial 7, 175-177. VII International Symposium on Mesozoic Terrestrial Ecosystems.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

unnamed possible enantiornithine (Cumbaa and Tokaryk, 1993)
Middle Cenomanian, Late Cretaceous
Belle Fourche Member of the Ashville Formation, Saskatchewan, Canada
Material- (SMNH P2077.66) distal metatarsal III
Comments- Cumbaa and Tokaryk (1993) referred to this as a "presumed enantiornithine". It was later described by Tokaryk et al. (1997) as a possible enantiornithine based on the lack of distal fusion. However, this is a primitive character, so it should be compared to other theropod metatarsi.
References- Cumbaa and Tokaryk, 1993. Early birds, crocodile tears, and fish tales: Cenomanian and Turonian marine vertebrates from Saskatchewan, Canada. Journal of Vertebrate Paleontology. 13(3), 31A-32A.
Tokaryk, Cumbaa and Storer, 1997. Early Late Cretaceous birds from Saskatchewan, Canada: the oldest diverse avifauna known from North America. Journal of Vertebrate Paleontology. 17(1), 172-176.

unnamed Enantiornithes (Buffetaut, 1998)
Late Campanian-Early Maastrichtian, Late Cretaceous
Massecaps, Herault, France
Material- (ACAP-M 192) incomplete coracoid
(ACAP-M 193) proximal femur
Comments- These were described by Buffetaut (1998) as enantiornithines and stated to resemble Enantiornis most closely. Walker et al. (2007) noted they could be referrable to the similarly sized Martinavis from the same strata, and described more precise similarities between ACAP-M 192 and Enantiornis, and ACAP-M 193 and unnamed Lecho Formation femora. Whether these similarities (reduced acrocoracoid; robust coracoid head; supracoracoid foramen does not open into dorsal fossa; well developed trochanteric crerst; deeply excavated proximolateral surface of femur) are synapomorphic requires further study.
References- Buffetaut, 1998. First evidence of enantiornithine birds from the Upper Cretaceous of Europe: Postcranial bones from Cruzy (Herault, Southern France). Oryctos. 1, 131-136.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

unnamed Enantiornithes (Kurochkin, 1999)
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Material- (PIN 4499-15) distal radius
(PIN 4499-16) distal ulna
(PIN 4499-18) distal carpometacarpus
Reference- Kurochkin, 1999. A new large enantiornithid from the Upper Cretaceous of Mongolia (Aves, Enantiornithes). Russian Academy of Sciences, Proceedings of the Zoological Institute 277: 130-141. [In Russian w/ English summary.]

unnamed enantiornithine (Schweitzer, Jackson, Chiappe, Calvo and Rubilar, 2001)
Santonian, Late Cretaceous
Bajo de la Carpa Formation of the Rio Colorado Subgroup, Neuquen, Argentina
Material- (MUCPv-284) coracoid, partial furcula, incomplete humerus, proximal radius, proximal ulna, ischia (~5 mm), distal femur, tibiae (one fragmentary), egg (45x27 mm)
(MUCPv-305) egg
(MUCPv-306) egg
(MUCPv-350) partial egg
(MUCPv-351) partial egg
(MUCPv-352) partial egg
(MUCPv-353) partial egg
(MUCPv-354) partial egg
(MUCPv-355) partial egg
Comments- Schweitzer et al. (2001, 2002) referred this specimen to Enantiornithes. The strut-like coracoid indicates these are ornithurine (sensu Gauthier) eggs, while the large proximodorsal ischial process is similar to non-ornithuromorph ornithurines. The laterally excavated furcula is only known in enantiornithines. The dorsally projected deltopectoral crest is unlike Aves as well as most more basal ornithuromorphs (except ambiortids, Gansus and Ichthyornis). The slender radius (compared to ulnar width) does not indicate bird affinities though, as it is also found in many more basal maniraptorans. The specimens could belong to the enantiornithine Neuquenornis from the same locality. While the prismatic structure of the eggshell was noted as being like neognaths, Gobipipus and troodontids are now known to have a similar construction. The third structural layer is otherwise unique to ornithuromorphs where definitely associated with skeletal material however.
References- Schweitzer, Jackson, Chiappe, Calvo and Rubilar, 2001. Cretaceous avian eggs and embryos from Argentina. Journal of Vertebrate Paleontology. 21(3), 99A.
Schweitzer, Jackson, Chiappe, Schmitt, Calvo and Rubilar, 2002. Late Cretaceous avian eggs with embryos from Argentina. Journal of Vertebrate Paleontology. 22(1), 191-195.

unnamed Enantiornithes (Osi, 2004)
Santonian, Late Cretaceous
Csehbanya Formation, Hungary
Material- (MTM Gyn.439) tarsometatarsus (51 mm)
(MTM V.2002.05) incomplete femur (22 mm)
Comments The femur was discovered in 2001 and the tarsometatarsus in 2002-2004. They were first briefly described by Osi (2004), then described in more detail as Enantiornithes indet. by Osi (2008). The specimens belong to different taxa, as the tarsometatarsus is from a much larger individual than the femur. Osi (2008) noted the tarsometatarsus is similar to Yungavolucris in its robusticity and has metatarsal IV longer than III. Though the latter was considered an apomorphy, it is also present in Longipteryx, Boluochia and Alethoalaornis. Osi (2004) also referred two other specimens to Enantiornithes (distal femur MTM V.2002.05 and distal metatarsal III MTM V.2003.19), but these were placed more generally as non-avian birds by him in 2008.
References- Osi, 2004. Enantiornithine bird remains from the Late Cretaceous of Hungary. Sixth International Meeting of the Society of Avian Palaeontology and Evolution, Abstracts. 50.
Osi, 2008. Enantiornithine bird remains from the Late Cretaceous of Hungary. Oryctos. 7, 55-60.

unnamed enantiornithine (Alvarenga and Nava, 2005)
Turonian-Santonian, Late Cretaceous
Adamantina Formation of the Bauru Group, Brazil
Material- (MZ coll.) vertebrae, ribs
References- Alvarenga, and Nava, 2005. Aves Enantiornithes do Cretaceo Superior da Formacao Adamantina do Estado de Sao Paulo, Brasil. II Congresso
Latino-Americano de Paleontologia de Vertebrados (Rio de Janeiro), Boletim de Resumos. p. 20.
Candeiro, Martinelli, Avilla and Rich, 2006. Tetrapods from the Upper Cretaceous (Turonian-Maastrichtian) Bauru Group of Brazil: a reappraisal. Cretaceous Research.

undescribed enantiornithine (Zheng, Zhang and Hou, 2007)
Early Aptian, Early Cretaceous
Qiaotou Member of the Huajiying Formation, Hebei, China
Material- (STM V001) incomplete skull, sclerotic ring, seven cervical vertebrae, incomplete coracoid, proximal humerus, body feathers
Comments- Zheng et al. (2007) state the skull of Paraprotopteryx' holotype "seems not to be the same individual as the postcranial bones after careful examination", and the portion of the slab containing the skull and cervical vertebrae does seem to contain an additional left coracoid.
Reference- Zheng, Zhang and Hou, 2007. A new enantiornithine bird with four long retrices from the Early Cretaceous of Northern Hebei, China. Acta Geologica Sinica. 81(5), 703-708.

Explorornis Panteleev, 1998
Diagnosis- (after Panteleev, 1998) coracoid shaft primitively not narrower than deep (also in Elsornis, walkeri and Catenoleimus).
(proposed) crest along the dorsolateral edge of the shaft (also in Eocathayornis).
Other diagnoses- Panteleev (1998) also listed the broad distal expansion in his diagnosis, but this is primitive for ornithothoracines. The low coracoid tubercle is not different from Incolornis, Otogornis or Neuquenornis. The gradually rising edge of the dorsal coracoid fossa is also present in walkeri, Incolornis, Elsornis, Shanweiniao, Sinornis and Eocathayornis. The coracoid glenoid facet is generally rather flat in enantiornithines, and is eroded in Explorornis nessovi, so Panteleev's characterization of a convex glenoid in the taxon seems questionable.
Comments- Panteleev also referred another species to this genus- E. walkeri. While walkeri shares the plesiomorphic dorsoventrally flattened coracoid shaft and shallow dorsal fossa of nessovi, there are no shared derived characters yet identified that could unite the species.
E. nessovi Panteleev, 1998
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 4819) (~165 mm) distally incomplete coracoid (18.8 mm)
Diagnosis- (proposed) compared to E. sp. nov., lateral and medial edges around dorsal coracoid fossa thin; coracoid shaft thinner; lateral edge of coracoid completely concave.
Comments- This was collected in 1991 and originally identified as Enantiornithes by Nessov and Panteleev (1993) and Nessov (1997). Panteleev (1998) and it and referred it to Alexornithidae within Alexornithiformes without comment. Nessov (1996) referred the then unnamed specimen to Alexornithidae based on the narrow shaft, shallow dorsal coracoid fossa and "slightly projected lateral margin". Yet Nessov's classification is flawed, as for instance his enantiornithid Enantiornis has a narrower shaft and less projected lateral margin than Explorornis, while his concornithids such as Iberomesornis and Sinornis are comparable in these regards, and the latter also has a shallow dorsal fossa. The coracoid fossa does indicate this is an enantiornithine, as Apsaravis differs in having a concave scapular facet. Within Enantiornithes, the concave lateral edge and shallow dorsal fossa may mean this is a relatively basal taxon.
References- Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Nessov, 1997. [Cretaceous nonmarine vertebrates of northern Eurasia]. Saint Petersburg, Institute of Earth Crust. 1-218.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.
E. sp. nov. (Panteleev, 1998)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 4818) (~165 mm) incomplete coracoid (~19 mm)
Diagnosis- (proposed) compared to E. nessovi, lateral and medial edges around dorsal coracoid fossa thick; coracoid shaft thicker; lateral; edge of coracoid distally convex.
Comments- This was originally identified as Enantiornithes by Nessov and Panteleev (1993) and Nessov (1997). It was described as Explorornis sp. 1 by Panteleev (1998), which seems valid since it has the apomorphic crest of that genus. However, the other shared character (shaft broader than deep) is plesiomorphic and the slightly convex laterodistal edge might indicate it is more derived. Kurochkin (1996) referred it to Alexornithiformes fam. indet. without justification.
References- Nessov and Panteleev, 1993. On the similarity of the Late Cretaceous ornithofauna of South America and Central Asia. Trudy Zoologicheskogo Instituta, RAN. 252, 84-94.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Nessov, 1997. [Cretaceous nonmarine vertebrates of northern Eurasia]. Saint Petersburg, Institute of Earth Crust. 1-218.
Panteleev, 1998. New species of enantiornithines (Aves: Enantiornithes) from the Upper Cretaceous of Central Kyzylkum. Russkii Ornitologicheskii Zhurnal. Ekspress-vy.pvsk 35: 3-15.

Noguerornis Lacasa-Ruiz, 1989
N. gonzalezi Lacasa-Ruiz, 1989
Late Berriasian-Early Barremian, Early Cretaceous
La Pedrera de Rubies Lithographic Limestones, Spain
Holotype- (LP.1702) last dorsal vertebra (1.6 mm), three dorsal rib fragments, first sacral vertebra (2 mm), second sacral vertebra (2.4 mm), incomplete furcula, humeri (22.8 mm), radii (23.1, 23.2 mm), ulna (24.3 mm), radiale, ulnare, carpometacarpus, proximal phalanx I-1, ischium, partial tibia, long bone shaft, coverts, secondary remiges
Diagnosis- ischial symphysis present.
References- Lacasa-Ruiz, 1986. Nota preliminar sobre el hallazgo de restos keos de un ave fosil en el yacimiento neocomiense del Montsec. (Prov .Lerida, Espafia). Ilerdu. 47, 203-206.
Lacasa-Ruiz, 1989. An Early Cretaceous fossil bird from Montsec Mountain (Lleida, Spain). Terra Nova. 1(1), 45-46.
Lacasa-Ruiz, 1989. Nuevo genero de ave fosil del yacimiento Neocomiense del Montsec (Provincia de Lerida, Espana). Estudios Geologicos. 45, 417-425.
Chiappe and Lacasa-Ruiz, 2002. Noguerornis gonzalezi (Aves: Ornithothoraces) from the Early Cretaceous of Spain. 230-239. in Chiappe and Witmer, (eds.). Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

Pengornis Zhou, Clarke and Zhang, 2008
P. houi Zhou, Clarke and Zhang, 2008
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V15336) skull (~54.7 mm), mandibles, eleven cervical vertebrae, few dorsal vertebrae, dorsal ribs, gastralia, synsacrum (~27.1 mm), six caudal vertebrae, proximal pygostyle, scapulae, coracoids (37.9 mm), incomplete furcula, humeri (64.3 mm), radii (66.7 mm), ulnae (70.7 mm), radiales, ulnares, carpometacarpi (34.3 mm; mcII 27 mm, mcIII 31.1 mm), phalanges II-1 (16.3 mm), phalanx II-2, phalanx III-1, manual ungual, ilium, partial pubes (~49.2 mm), femora (48 mm), tibiotarsi (50.4 mm), fibula (~44.5 mm), metatarsal I (8.7 mm), pedal ungual I, tarsometatarsi (26.5 mm), phalanx II-1 (5.9 mm), phalanx II-2 (8.1 mm), pedal ungual II (12.4 mm), phalanx III-1 (8.6 mm), phalanx III-2 (7.9 mm), phalanx III-3 (8.8 mm), pedal ungual III (11.7 mm), phalanx IV-1 (5.2 mm), phalanx IV-2 (~3.8 mm), phalanx IV-3 (4.1 mm), phalanx IV-4 (5.9 mm), pedal ungual IV (9.9 mm), ungual
Diagnosis- (after Zhou et al., 2008) premaxillae unfused; hooked scapular acromion; globose humeral head that projects further proximally than the deltopectoral crest.
Comments- Zhou et al. (2008) found Pengornis to be more derived than Protopteryx, but outside a clade containing Concornis, Gobipteryx, Neuquenornis and Sinornis when entered into Clarke's matrix.
Reference- Zhou, Clarke and Zhang, 2008. Insight into diversity, body size and morphological evolution from the largest Early Cretaceous enantiornithine bird. Journal of Anatomy. 212, 565-577.

Protopterygiformes Zhang and Zhou, 2006
Protopterygidae Zhang and Zhou, 2006
Protopteryx Zhang and Zhou, 2000
P. fengningensis Zhang and Zhou, 2000
Late Hauterivian, Early Cretaceous
Sichakou Sedimentary Member of the Huajiying Formation, Hebei, China
Holotype- (IVPP V11665) (~130 mm; juvenile?) skull (28.3 mm), mandible, seven or eight cervical vertebrae (18.5), twelve dorsal vertebrae (33.9 mm), dorsal ribs, sacrum, seven free caudal vertebrae (9.4 mm), pygostyle (11.3 mm), scapulae (21.7 mm), coracoids, furcula (14.7 mm), sternum, humeri, radii, ulnae, semilunate carpal, distal carpal III, metacarpal I, phalanx I-1, manual ungual I, metacarpal II, phalanx II-1, phalanx II-2, manual ungual II, metacarpal III, phalanx III-1, phalanx III-2, ilium (15.3 mm), pubis (22.3 mm), ischium (12.9 mm), femur (19 mm), tibia, fibula, astragalus, calcaneum, distal tarsal, tarsometatarsus, pedal phalanges, pedal unguals, feather impressions
Paratype- (IVPP V11844) (~130 mm; juvenile?) incomplete skeleton including skull, mandible, seven or eight cervical vertebrae (19.1), twelve dorsal vertebrae (34 mm), dorsal ribs, seven free caudal vertebrae, pygostyle, coracoids (12.7 mm), furcula (14 mm), sternum (15.9 mm), sternal ribs, forelimbs, ilium (14.8 mm), feather impressions
Diagnosis- (proposed) scapulocoracoid articulation flat; procoracoid process; wide interclavicular angle (ontogenetic?); carpometacarpus unfused (ontogenetic?); distal tarsals unfused to tarsometatarsus (ontogenetic?).
Comments- Jin et al. (2008) reidentified the horizon of Protopteryx as the Huajiying Formation, instead of the Yixian Formation as stated by Zhang and Zhou (2000) or the Dabeigou Formation as in Zhang et al. (2008).
References- Zhang and Zhou, 2000. A primitive enantiornithine bird and the origin of feathers. Science. 290, 1955-1959.
Jin, Zhang, Li, Zhang, Li and Zhou, 2008. On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota. Chinese Science Bulletin. 53(18), 2820-2827.
Zhang, Zhou and Benton, 2008. A primitive confuciusornithid bird from China and its implications for early avian flight. Science in China Series D: Earth Sciences. 51(5), 625-639.

unnamed clade

Alexornithiformes Brodkorb, 1976
Alexornithidae Brodkorb, 1976
Alexornis Brodkorb, 1976
A. antecedens Brodkorb, 1976
Campanian, Late Cretaceous
Bocana Roja Formation, Mexico
Holotype- (LACM 33213) distal humerus (~105 mm)
Paratypes- ....(LACM 32213) proximal scapula, proximal coracoid (~12 mm), distal humerus, proximal ulna, distal femur, proximal tibia, fragments
Diagnosis- anterior cnemial crest present.
Reference- Brodkorb, 1976. Discovery of a Creteceous bird, apparently ancestral to the orders Coraciiformes and Piciformes (Aves: Carinatae). pp 67-73. in Olson (ed.). Collected papers in avian phylogeny honoring the 90th birthday of Alaxander Wetmore. Smithsonian Contributions to Paleobiology. No. 27.

"Bohaiornis" Hu, Hou and Xu, 2009
"B. guoi" Hu, Hou and Xu, 2009
Barremian-Aptian, Early Cretaceous
Yixian Formation, Liaoning, China
Material- (LPM-B00167) complete skeleton including skull, mandible, cervical vertebrae, synsacrum, scapula, coracoid, furcula, sternum, forelimbs, hindlimbs and feathers
Diagnosis- (after Hu et al., 2009) sacral centra strongly compressed transversely; acromion twice as long as glenoid facet; clavicular ramus of furcula straight; clavular facet with a transversely expanded proximal end; prominent ridge along medioventral margin of clavicular ramus of furcula.
Other diagnoses- Hu et al. (2009) state the presence of cervical centra with strong ventral keels is unique, but this is shared with most other enantiornithines except Pengornis.
Comments- Hu et al. (2009) briefly describe this new taxon in their SVP abstract, which makes it a nomen nudum according to ICZN Article 9.9. While the authors state "Bohaiornis" strongly resembles Eoenantiornis in several characters (short and deep skull with six to seven teeth on each side of upper and lower jaws; forelimbs subequal to hindlimbs in length; manual digit I with robust and curved ungual extending distally to the level of the distal end of metacarpal II), only the short and deep skull is potentially synapomorphic. Their phylogenetic analysis found "Bohaiornis" to be more derived than Protopteryx, but more basal than most other enantiornithines including Eoenantiornis.
Reference- Hu, Hou and Xu, 2009. A new enantiornithine bird from the Lower Cretaceous of Western Liaoning, China. Journal of Vertebrate Paleontology. 29(3), 118A.

Halimornis Chiappe, Lamb and Ericson, 2002
H. thompsoni Chiappe, Lamb and Ericson, 2002
Early-Middle Campanian, Late Cretaceous
Mooreville Chalk Formation, Alabama, US
Holotype- (D2K 035) two dorsal vertebrae, caudal vertebra, pygostyle, proximal humerus, distal femur
....(UAMNH PV996.1.1) dorsal centrum, dorsal neural arch, proximal scapula
Reference- Chiappe, Lamb and Ericson, 2002. New enantiornithine bird from the marine Upper Cretaceous of Alabama. Journal of Vertebrate Paleontology. 22(1), 170-174.

Kizylkumavis Nessov, 1984
K. cretacea Nessov, 1984
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (TsNIGRI 51/11915) (~110 mm) distal humerus (~27 mm)
Reference- Nessov, 1984. [Upper Cretaceous pterosaurs and birds from Central Asia] Paleontologicheskii Zhurnal. 1, 47-57.

Sazavis Nessov vide Nessov and Jarkov, 1989
S. prisca Nessov vide Nessov and Jarkov, 1989
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Holotype- (PO 3472) (~185 mm) distal tibiotarsus (4.5 mm wide)
References- Nessov and Jarkov, 1989. New Cretaceous-Paleogene birds of the USSR and some remarks on the origin and evolution of the class Aves. Proceedings of the Zoological Institute, Leningrad. 197, 78-97. (in Russian).
Elzanowski, 1995. Cretaceous birds and avian phylogeny. Cour. Forschungsinst. Senckenb. 181, 37-53.

Longipterygiformes Zhang, Zhou, Hou and Gu, 2001
Longipterygidae Zhang, Zhou, Hou and Gu, 2001
Definition- (Longipteryx chaoyangensis + Longirostravis hani) (O'Connor, Wang, Chiappe, Gao, Meng, Cheng and Liu, 2009)
Longipteryx Zhang, Zhou, Hou and Gu, 2001
L. chaoyangensis Zhang, Zhou, Hou and Gu, 2001
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V12325) (~190 mm) skull (55.06 mm), mandible, hyoids, seven cervical vertebrae, at least five dorsal vertebrae, sixteen dorsal ribs, ten uncinate processes, six rows of gastralia, sacrum, six caudal vertebrae, pygostyle (21.38 mm), scapulae, incomplete coracoids (19.86 mm), furcula, sternal fragments, four sternal ribs, incomplete humeri (43.48, ~42.03 mm), incomplete radii (~43.48 mm), incomplete ulnae (44.26, ~47.1 mm), radiale, ulnare, semilunate carpal, metacarpal I (4.4 mm), phalanx I-1 (8.5 mm), manual ungual I (7.7 mm), metacarpal II (17 mm), phalanx II-1 (10 mm),phalanx II-2 (9.3 mm), manual ungual II (8.5 mm), metacarpal III (18 mm), phalanx III-1 (5.1 mm), phalanx III-2 (1.5 mm), ilia, incomplete pubes, incomplete ischium, incomplete femora (28.26, 28.77 mm), incomplete tibiae (30.07 mm), fibulae (12 mm), proximal tarsals, metatarsal I (4.8 mm), phalanx I-1, pedal ungual I, tarsometatarsus (metatarsal II 20 mm; III 20.5 mm; IV 21 mm), phalanx II-1, phalanx II-2, phalanx III-1, proximal phalanx III-2, phalanges from digit IV, feather impressions
Paratypes- (IVPP V12552) complete skeleton including sternum
(IVPP V12553) furcula, humerus
(IVPP V12554) ulna
Diagnosis- scapula distally broad; wide interclavicular angle (ontogenetic?); metatarsal IV longer than III (also in Boluochia and Alethoalaornis).
Reference- Zhang, Zhou, Hou and Gu, 2001. Early diversification of birds: Evidence from a new opposite bird. Chinese Science Bulletin. 46(11), 945-950.

Longirostravisiformes Zhou and Zhang, 2006
Longirostravisidae Zhou and Zhang, 2006
Diagnosis- manual ungual I absent; manual ungual II absent; longitudinal crest on the central portion of its pedal unguals' sides.

Shanweiniao O'Connor, Wang, Chiappe, Gao, Meng, Cheng and Liu, 2009
S. cooperorum O'Connor, Wang, Chiappe, Gao, Meng, Cheng and Liu, 2009
Early Aptian, Early Cretaceous
Dawangzhangzi Beds of Yixian Formation, Liaoning, China
Holotype- (DMNH D1878) (adult) skull (31.36 mm), sclerotic ring, mandibles, nine cervical vertebrae, six dorsal vertebrae, partial dorsal ribs, gastralia, partial synsacrum, several caudal vertebrae, pygostyle (12.37 mm), scapula, coracoids (~12.61 mm), furcula (~8.95 mm), sternum, sternal ribs, humeri (~21.31, 22.43 mm), radii (~22.53 mm), ulnae (~23.36 mm), partial proximal carpal, phalanx I-1, manual ungual I, partial metacarpal II, phalanges II-1 (4.55 mm), phalanges II-2 (2.62 mm), phalanx III-1 (2.33 mm), partial ilium, partial pubes, femora (~17.6 mm), tibiotarsi (22.61, 22.41 mm), fibula, partial metatarsals I, phalanges I-1 (3.71 mm), pedal unguals I, tarsometatarsi (11.9, 11.75 mm; mtII 9.3, 10.05 mm, mtIII 11.16, 20.84 mm, mtIV 10.98, 10.72 mm), phalanges II-1 (2.75 mm), phalanges II-2 (4.4, 4.44 mm), pedal unguals II (6.51, 6.54 mm), phalanges III-1 (~2.71 mm), phalanges III-2 (2.98 mm), phalanges III-3 (~3.99 mm), pedal unguals III (~5.67, 5.19 mm), phalanges IV-1 (1.82 mm), phalanges IV-2 (1.28 mm), phalanges IV-3 (2.15 mm), phalanges IV-4 (3.23 mm), pedal unguals IV (~5.54, 5.8 mm), pedal claw sheaths, body feathers, remiges, retrices
Diagnosis- (after O'Connor et al., 2009) intermembral index (humerus+ulna/.femur+tibiotarsus) 1.23.
Other diagnoses- O'Connor et al. (2009) also list several other characters in the diagnosis which they state are found in related taxa as well. The snout length (62% of skull length) is overlapped by Longirostravis (60-64%) and very similar to Longipteryx (64%) and Rapaxavis (65%). Manual phalanx II-2 is reduced and wedge-shaped in Longirostravis and Rapaxavis too. The low interclavicular angle (~40 degrees) is also present in Iberomesornis and Concornis. The length of the hypocleideum being shorter than the interclavicular symphysis is not necessarily true, as the authors state the hypocleideal length is unknown. The distallly non-branched posterolateral sternal processes are plesiomorphic for enantiornithines. Metatarsal III is longest plesiomorphically for theropods. O'Connor et al. note Rapaxavis also has a longitudinal crest on the central portion of its pedal unguals' sides. Two pairs of elongate retrices are also present in Paraprotopteryx. The pedal ungual and claw curvature is similar to that of Rapaxavis.
Reference- O'Connor, Wang, Chiappe, Gao, Meng, Cheng and Liu, 2009. Phylogenetic support for a specialized clade of Cretaceous enantiornithine birds with information from a new species. Journal of Vertebrate Paleontology. 29(1), 188-204.

unnamed clade (Longirostravis hani + Rapaxavis pani)
Diagnosis- less than eight sacral vertebrae; posterolateral sternal process with tribranched distal tip.

Longirostravis Hou, Chiappe, Zhang and Chuong, 2004
= "Longirostravis" Hou, Chiappe, Zhang and Chuong, 2003 online
L. hani Hou, Chiappe, Zhang and Chuong, 2004
= "Longirostravis hani" Hou, Chiappe, Zhang and Chuong, 2003 online
Late Barremian-Early Aptian, Early Cretaceous
Jianshangou or Dawangzhangzi Beds of Yixian Formation, Liaoning, China
Holotype- (IVPP V11309) (~105 mm) skull (~32.86 mm), mandibles, cervical vertebrae, dorsal vertebrae, dorsal ribs, gastralia, sacrum, five caudal vertebrae, pygostyle (13.57 mm), scapulae (19.2 mm), coracoids (13.57, ~11.86 mm), furcula (10.71 mm), sternum (17 mm), humeri (23.51, ~25.71 mm), radii (~21.43, 24.57 mm), ulnae (~24.11, ~25.14 mm), proximal carpal, carpometacarpus, manual phalanges?, ilium (13.8 mm), pubis, ischium, femora (19.43 mm), tibiotarsi (25.17, 25 mm), fibulae, metatarsal I, tarsometatarsus (13.74 mm), pedal phalanges, feather impressions
Diagnosis- (after Hou et al., 2004) posterolateral sternal process with cladogram-like three-branched distal end.
(proposed) seven sacral vertebrae (also in Protopteryx).
Other diagnoses- Hou et al. (2004) included two other characters in their diagnosis. The long tapered snout is also present in Longipteryx, Shanweiniao and Rapaxavis, while Longipteryx's and Rapaxavis' are also decurved. Shanweiniao and Rapaxavis share dentation which is as anteriorly limited.
Comments- The description was first published online on December 17, 2003. However, at present the ICZN does not recognize electronic publication to be valid, so the citation must be for 2004, when the issue was published on paper.
References- Hou, Chiappe, Zhang and Chuong, 2004. New Early Cretaceous fossil from China documents a novel trophic specialization for Mesozoic birds. Naturwissenschaften. 91(1), 22-25.
Zhou and Zhang, 2006. Mesozoic birds of China- A synoptic review. Vertebrata PalAsiatica. 44(1), 60-98.

Rapaxavis Morschhauser, Varricchio, Gao, Liu, Wang, Cheng and Meng, 2009
R. pani Morschhauser, Varricchio, Gao, Liu, Wang, Cheng and Meng, 2009
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (DMNH D2522) (subadult) skull, mandibles, hyoid, eight or nine cervical vertebrae, dorsal vertebra, ten dorsal ribs, six gastralia, synsacrum, six caudal vertebrae, pygostyle, anterior scapula, coracoids, furcula, parasternal elements, sternum, ten sternal ribs (4.7-9.7 mm), humeri, radii, ulnae, ulnares, metacarpals I, phalanges I-1, metacarpals II, phalanges II-1, phalanges II-2, metacarpals III, phalanges III-1, phalanges III-2, ilia, pubes, ischia, femora, tibiae, fibulae, astragalocalcanea, distal tarsals III, distal tarsals IV, metatarsals I, phalanges I-1, pedal unguals I, tarsometatarsi, phalanges II-1, phalanges II-2, pedal unguals II, phalanges III-1, phalanges III-2, phalanges III-3, pedal unguals III, phalanges IV-1, phalanges IV-2, phalanges IV-3, phalanges IV-4, pedal unguals IV, pedal claw sheaths
Diagnosis- (after Morschhauser et al., 2009) six sacral vertebrae; posterolateral sternal processes with two prominent branches and a smaller third branch; parasternal elements.
Other diagnoses- Morschhauser et al. (2009) list several other characters in their diagnosis as well. The long and slightly curved snout is also present in Longipteryx and Longirostravis. Shanweiniao seems to have as few dentary teeth as Rapaxavis. Boluochia, Dapingfangornis, Jibeinia, Longipteryx, Pengornis and Sinornis also have six free caudal vertebrae. The lack of Longirostravis' antler-shaped posterolateral sternal processes is plesiomorphic, as is the unexpanded posteromedian sternal process. The lack of manual unguals I and II is shared with Longirostravis and Shanweiniao. Having hindlimbs longer compared to the forelimbs than in Longipteryx is plesiomorphic, with Longirostravis having a similar ratio. Longirostravis has a similarly long hallux compared to tarsometatarsal length, as opposed to Longipteryx and Shanweiniao.
Comments- This specimen was first reported by Morschhauser et al. (2006) as a juvenile Longirostravis or a new related taxon, and was used in the phylogenetic analysis of O'Connor et al. (2009) before it was named. This found it to be a longipterygid sister to Longirostravis (though it was misspelled DMNH D2567/8 in figure 8 and switched with Zhongornis), which Morschhauser et al. (2009) agreed with when they named and described the taxon a few months later.
References- Morschhauser, Liu, Meng and Varricchio, 2006. Anatomical details from a well preserved specimen of Longirostravis (Aves, Enantiornithes) from the Jiufotang Formation, Liaoning Province, China. Journal of Vertebrate Paleontology. 26(3), 103A.
Morschhauser, Varricchio, Gao, Liu, Wang, Cheng and Meng, 2009. Anatomy of the Early Cretaceous bird Rapaxavis pani, a new species from Liaoning Province, China. Journal of Vertebrate Paleontology. 29(2), 545-554.
O'Connor, Wang, Chiappe, Gao, Meng, Cheng and Liu, 2009. Phylogenetic support for a specialized clade of Cretaceous enantiornithine birds with information from a new species. Journal of Vertebrate Paleontology. 29(1), 188-204.

unnamed clade

Alethoalaornithidae Li, Hu, Duan, Gong and Hou, 2007
Alethoalaornis Li, Hu, Duan, Gong and Hou, 2007
A. agitornis Li, Hu, Duan, Gong and Hou, 2007
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (LPM 00009) incomplete skull (27 mm), mandible, nine cervical vertebrae, nine dorsal vertebrae, dorsal rib fragments, six caudal vertebrae, pygostyle (16 mm), scapulae, coracoids, furcula, sternum, humeri (24 mm), radii, ulnae (26 mm), radiales, ulnares, carpometacarpi (23 mm), phalanges I-1, manual unguals I, phalanges II-1 + III-1, phalanges II-2, manual unguals II, pubes, femora (24 mm), tibiotarsi (27 mm), fibula, phalanx I-1, pedal ungual I, tarsometatarsi (17 mm), phalanx II-1, phalanx II-2, pedal ungual II, phalanges III-1, phalanges III-2, phalanges III-3, pedal ungual III, phalanges IV-1, phalanges IV-2, phalanges IV-3, phalanges IV-4, pedal unguals IV, body feathers, remiges
Paratypes- (LPM 00032) specimen including synsacrum, pygostyle, humeri, radius, ulnae, carpometacarpus, phalanx I-1, femur, tibiotarsu, phalanx I-1, pedal ungual I, tarsometatarsus, phalanx II-1, phalanx II-2, pedal ungual II, phalanx IIi-1, phalanx III-2, phalanx III-3, pedal ungual III, phalanx IV-1, phalanx Iv-2, phalanx IV-3, phalanx IV-4, pedal ungual IV
(LPM 00038) specimen including skull, cervical vertebrae, dorsal vertebrae, dorsal ribs, synsacrum, pectoral elements, humeri, radii, ulnae, carpometacarpi, phalanges I-1, manual ungual I, phalanges II-1, phalanges II-2, phalanges III-1, partial ilia, pubis(?), femora, tibiotarsi, metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsi, pedal phalanges, pedal unguals
(LPM 00040) specimen including skull, mandibles, cervical vertebrae, dorsal vertebrae, pectoral elements, humeri, radii, ulnae, manus, femur, tibiotarsus, fibula, pedal digits I, tarsometatarsi, pedal phalanges, pedal unguals
(LPM 00053) specimen including dorsal ribs, gastralia, synsacrum, caudal vertebrae, pygostyle, incomplete humerus, radius, ulna, partial carpometacarpus, phalanx II-1, ilium, pubis, femora (one partial), tibiotarsi (one incomplete), fibula, metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsus, phalanx II-1, phalanx II-2, pedal ungual II, phalanx III-1, phalanx III-2, phalanx IIII-3, pedal ungual III, pedal digit IV
Diagnosis- (after Li et al., 2007) hypcleidium equals clavular ramus in length; humerus with pneumatic foramina.
Comments- Li et al. (2007) named this taxon in a description which was largely published in Chinese, with only a short English summary. They erected the new family Alethoalaornithidae for the genus, which they placed in Cathayornithiformes. This latter assignment was based on "similar length of trochlea at distal end of tarsometatarsus." If this refers to equal width, it is unlike Sinornis (= Cathayornis), which has trochlea II widest, and if it refers to distal extent, it is also unlike Sinornis which has trochlea III longest (whereas Alethoalaornis has trochlea IV longest).
Other diagnoses- Li et al. (2007) listed numerous other characters in their diagnosis of Alethoalaornis and Alethoalaornithidae. The beak does not seem longer than most enantiornithines, while its apparent sharpness in LPM 00038 is due to preparation and that of LPM 00040 could be due to that or preservation. Two to three pairs of premaxillary teeth seem to be present in Pengornis. Heterocoelous cervical vertebrae and thin hypocleidia are present in most enantiornithines. A "well developed" sternal carina and "metacarpal formed" are too vague to evaulate. Deep capital grooves are present in all enantiornithines except Elsornis. The manual unguals on digits I and II are reduced a similar amount in Hebeiornis and Shanweiniao, while many derived enantiornithines lack an ungual on digit III. Contra their description, the illustration suggests that the metatarsals increase in length laterally instead of being equally long. This is also present in Longipteryx and Boluochia. Pedal unguals are longer than their pedal phalanges in most enantiornithines, including Pengornis, Shanweiniao and Sinornis.
Reference- Li, Hu, Duan, Gong and Hou, 2007. Alethoalaornithidae fam. nov.: A new family of enantiornithine bird from the Lower Cretaceous of Western Liaoning. Acta Palaeontologica Sinica. 46(3), 365-372.

Gurilynia Kurochkin, 1999
G. nessovi Kurochkin, 1999
Late Campanian-Early Maastrichtian, Late Cretaceous
Nemegt Formation, Mongolia
Holotype- (PIN 4499-12) proximal humerus
Paratypes- ....(PIN 4499-13) (~510 mm) proximal coracoid (~58 mm)
....(PIN 4499-14) distal humerus
Reference- Kurochkin, 1999. A new large enantiornithid from the Upper Cretaceous of Mongolia (Aves, Enantiornithes). Russian Academy of Sciences, Proceedings of the Zoological Institute 277: 130-141. [In Russian w/ English summary.]

Avisauridae Paul and Brett-Surman, 1985
Definition- (Avisaurus archibaldi + Neuquenornis volans) (Chiappe, 1993)
Other definitions- (Avisaurus archibaldi <- Longipteryx chaoyangensis, Sinornis santensis, Gobipteryx minuta) (Cau and Arduini, 2008)
References- Brett-Surman and Paul, 1985. A new family of bird-like dinosaurs linking Laurasia and Gondwanaland. Journal of Vertebrate Paleontology. 5(2), 133-138.
Chiappe, 1993. Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates. 3083, 39 pp.
Cau and Arduini, 2008. Enantiophoenix electrophyla gen. et sp. nov. (Aves, Enantiornithes) from the Upper Cretaceous (Cenomanian) of Lebanon and its phylogenetic relationships. Atti Soc. it. Sci. nat. Museo civ. Stor. nat. Milano. 149(II), 293-324.
Avisaurus Brett-Surman and Paul, 1985
A. archibaldi Brett-Surman and Paul, 1985
Late Maastrichtian, Late Cretaceous
Hell Creek Formation, Montana, US
Holotype- (UCMP 117600) (~550 mm) tarsometatarsus (73.9 mm)
Paratype- (PU 17324) tarsometatarsus
References- Brett-Surman and Paul, 1985. A new family of bird-like dinosaurs linking Laurasia and Gondwanaland. Journal of Vertebrate Paleontology. 5(2), 133-138.
A. gloriae Varricchio and Chiappe, 1995
Middle-Late Campanian, Late Cretaceous
Two Medicine Formation, Montana, US
Holotype- (MOR 553E/6.19.91.64) (~230 mm) tarsometatarsus (30.9 mm)
Comments- This taxon was first referred to as the Two Medicine form in Chiappe (1993).
References- Chiappe, 1993. Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates. 3083, 39 pp.
Varricchio and Chiappe, 1995. A new enantiornithine bird from the Upper Cretaceous Two Medicine Formation of Montana. Journal of Vertebrate Paleontology. 15(1), 201-204.
A. sp. (Stidham, 1999)
Late Maastrichtian, Late Cretaceous
Hell Creek Formation, Montana, US
Material- (juvenile) distal tarsals, metatarsus
References- Stidham, 1999. North American avisaurids (Aves: Enantiornithes): New data on morphology and phylogeny. VII International Symposium on Mesozoic Terrestrial Ecosystems, abstracts.
Stidham, 2002. Evolutionary and developmental origin of the extant bird tarsometatarsus from its theropod dinosaur ancestry. Journal of Vertebrate Paleontology. 22(3), 111A.

Boluochiformes Zhou and Zhang, 2006
Boluochidae Zhou and Zhang, 2006
Boluochia Zhou, 1995
B. zhengi Zhou, 1995
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V9770) (~155 mm; adult) premaxilla, partial nasals, partial dentary, tooth, two partial dorsal ribs, incomplete sacrum, six caudal vertebrae, pygostyle (21.5 mm), posterior sternum, two sternal ribs?, posterior ilium, pubis (23.1 mm), ischium (~16 mm), partial femora, tibiotarsi (~37 mm), metatarsal I (4.1 mm), tarsometatarsi (metatarsal II 17.2 mm, metatarsal III 17.4 mm, metatarsal IV 17.5 mm), pedal phalanges, pedal unguals
Diagnosis- premaxilla markedly convex anterodorsally and sigmoid ventrally, forming raptorial beak; posterior premaxillary process expanded; pygostyle distally expanded; highly bowed pubic shaft; deep extensor groove on femur; cnemial crest absent; metatarsals increase in length laterally (also in Longipteryx and Alethoalaornis).
Comments- This specimen was found by Zhou in 1990 along with the holotype of Cathayornis and an unidentified sternal impression (IVPP V 9941). It is mostly preserved as a natural mold. The completely fused synsacrum and pygostyle indicate it was an adult.
References- Zhou, 1995. Discovery of a new enantiornithine bird from the Early Cretaceous of Liaoning, China. Vertebrata PalAsiatica. 33(2), 99-113.
Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Zhou and Hou, 2002. The Discovery and Study of Mesozoic Birds in China. pp 160-183. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

"Cathayornis" aberransis Hou, Zhou, Zhang and Gu, 2002
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V12353) skull, gastralia, coracoids, incomplete furcula?, sternum, forelimb elements, carpometacarpi, pubes, proximal tibia, fibula, numerous other elements
Comments- Described by Hou et al. (2002) in a book which has not yet been translated to English, making information on this specimen extremely limited. Of the characters in the original diagnosis, toothed jaws, a well developed posteriorly distributed sternal keel, humerus slightly shorter than ulna and distally fused pubes are all plesiomorphic for Enantiornithes. Sinornis santensis (the senior synonym of Cathayornis yandica) only differs from these in that its ulna is slightly shorter than its humerus, but variations of 5-10% are known for other basal birds, so this doesn't guarantee a valid distinguishing characteristic. The longitudinal ridge between the frontals, and tubercles on "both sides of the frontal" are difficult to evaluate given taphonomy and the lack of frontal description and preservation in most enantiornithines. The last proposed diagnostic feature- posterolateral sternal processes shorter than posteromedian processes, does appear to be valid. This is also present in Protopteryx, probably Elsornis, Eoenantiornis and Hebeiornis though.
Reference- Hou, Zhou, Zhang and Gu, 2002. Mesozoic birds from western Liaoning in China. ISBN 7-5381-3392-5. 120 pp.

"Cathayornis" caudatus Hou, 1997
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V10917) skull (28 mm), mandible (~21 mm), four or five dorsal vertebrae, gastralia, sacral vertebrae, twenty-six caudal vertebrae, scapula, coracoid, incomplete sternum (21.5 mm), humeri (26 mm), incomplete radii (~25 mm), incomplete ulnae (26 mm), ulnare, carpometacarpus (15 mm), manual ungual (2 mm), partial ilium, partial pubis, femora (23 mm), tibiotarsi (27 mm), fibula (~7 mm), pedal ungual I (5 mm), tarsometatarsi (17 mm), pedal phalanges, pedal unguals
Paratypes- ?(IVPP V10533) dorsal vertebrae 9-11, sacrum (15.5 mm), caudal vertebrae, pygostyle, ilia (13 mm), pubes, ischium, femora (24.5 mm), tibiotarsi (30.5 mm), fibulae (9 mm), tarsometatarsi (16 mm), pedal phalanges, pedal unguals (5 mm)
?(IVPP V10904) gastralia, tibiotarsi (34.5 mm), fibula, tarsometatarsi (19 mm), pedal phalanges, pedal unguals (8 mm)
Diagnosis- unfused distal caudal vertebrae (ontogenetic?); laterally straight coracoid (ontogenetic?).
Comments- Clarke (2002) notes gastralia are present in the holotype (which she called Cathayornis yandica).
References- Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Clarke, 2002. The morphology and systematic position of Ichthyornis Marsh and the phylogenetic relationships of basal Ornithurae. Ph.D. dissertation, Yale University, New Haven, CT, 532 pp.

"Cathayornis" chabuensis Li, Li, Zhang, Zhou, Bai, Zhang and Ba, 2008
Early Cretaceous
Jingchuan Formation, Inner Mongolia, China
Holotype- (BMNHC-Ph000110) (subadult) ten cervical vertebrae, two cervical ribs, six dorsal vertebrae, nine dorsal ribs, scapulae (one incomplete), coracoids, sternum, humeri (one incomplete; 34 mm) radii (31 mm), ulnae (33 mm), carpometacarpi (one incomplete; 15 mm), phalanx II-1, phalanx II-2, phalanx III-1, femora (30 mm), tibiotarsi (38 mm), metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsi (one partial; 19 mm), phalanx II-1, phalanx II-2, pedal ungual II, phalanx III-1, phalanx III-2, phalanx III-3, pedal ungual III, feathers
Other diagnoses- Li et al. (2008) use the posteriorly diverging posterolateral sternal processes to distinguish this species from Sinornis santensis (their Cathayornis yandica), but this is true of most enantiornithines (e.g. Alethoalaornis, Boluochia, "Cathayornis" caudatus, Concornis, Dapingfangornis, Elsornis, Eocathayornis, Eoenantiornis, Hebeiornis, Jibeinia). The authors also distinguished it by its posteromedian sternal process which extends posteriorly past the posterolateral processes. This is also found in Protopteryx, Eocathayornis, Eoenantiornis, Hebeiornis, Shanweiniao and probably Elsornis.
Comments- Li et al. discovered this specimen in 2002 and described it as a new species of Cathayornis (= Sinornis) in 2008. They assigned it to Cathayornis based on several characters. The longitudinal radius groove is present in all enantiornithines more derived than Longipteryx. Sinornis actually has a broad intermetacarpal space (contra Li et al.), with the illusion of a nearly absent space in some enantiornithines due to postmortem distortion of the flattened third metacarpal. Several other enantiornithines have only one phalanx on manual digit III (Alethoalaornis, Concornis, Eoalulavis, Eoenantiornis, Gobipteryx, Hebeiornis), which is similar to Sinornis' in being closely appressed to phalanx II-1 when articulated (e.g. Eoalulavis, Hebeiornis) and is actually fused in Alethoalaornis based on its figure. Finally, Li et al. state "proportions of limb bones" are similar between Sinornis and chabuensis. The ulnohumeral ratios are indeed quite similar (98% vs. 97%), but so are those of "Cathayornis" caudatus (100%), Rapaxavis (100%) and Longirostravis (98%). The humerofemoral ratio of chabuensis (113%) is similar to Sinornis (114-117%), but so are "Cathayornis" caudatus (113%) and Eoenantiornis (111%). The tibiofemoral ratio of 127% is again close to Sinornis' (124-126%), but so are Dapingfangornis (126%), Jibeinia (126%), Shanweiniao (128%) and Longirostravis (129%). The tarsometatarsofemoral ratio of 63% is actually very low compared to Sinornis (70%), with many enantiornithines having ratios closer to Sinornis (67-73% in Alethoalaornis, Dapingfangornis, Hebeiornis, Jibeinia, Largirostrornis, Liaoxiornis, Shanweiniao, Longirostravis, Longipteryx, Iberomesornis and Cuspirostrisornis). Thus there are no unique shared characters with Sinornis and while the limb proportions are mostly similar, they are not necessarily derived. It is here excluded from Sinornis, though further study will be needed to determine which taxa it is most closely related to.
Reference- Li, Li, Zhang, Zhou, Bai, Zhang and Ba, 2008. A new species of Cathayornis from the Lower Cretaceous of Inner Mongolia, China and its stratigraphic significance. Acta Geologica Sinica. 82(6), 1115-1123.

Concornithidae Kurochkin, 1996
Concornis Sanz and Buscalioni, 1992
C. lacustris Sanz and Buscalioni, 1992
Late Barremian, Early Cretaceous
Calizas de La Huerguina Formation, Spain
Holotype- (LH-2814) (~130 mm) four posterior dorsal vertebrae, dorsal rib fragments, posterior sacrum, first caudal vertebra, second caudal vertebra, partial scapulae, coracoids, furcula, sternum, sternal ribs, humerus, incomplete radius, incomplete ulna, carpometacarpus, phalanx I-1, manual ungual I, phalanx II-1, phalanx II-2, manual ungual II, phalanx III-1, pubes, ischia, femora (24 mm), tibiotarsi (36 mm), metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsus (22 mm), phalanx II-1, phalanx II-2, partial pedal ungual II, proximal phalanx III-1, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV, feather impressions
References- Sanz and Buscalioni, 1992. A New Bird from the Early Cretaceous of Las Hoas, Spain, and the Early Radiation of Birds. Palaeontology, 35. 829-845.
Sanz, Chiappe and Buscalioni 1995. The Osteology of Concornis lacustris (Aves: Enantiornithes) from the Lower Cretaceous of Spain and a Reexamination of its Phylogenetic Relationships. American Museum Novitates. 3133, 1-23.
Sanz, Pérez-Moreno, Chiappe and Buscalioni, 2002. The Birds from the Lower Cretaceous of Las Hoyas (Privince of Cuenca, Spain). pp 209-229. in Chiappe and Witmer (eds.). Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

Dalingheornis Zhang, Hou, Hasegawa, O'Connor, Martin and Chiappe, 2006
D. liweii Zhang, Hou, Hasegawa, O'Connor, Martin and Chiappe, 2006
Early Aptian, Early Cretaceous
Dawangzhangzi Beds of Yixian Formation, Liaoning, China
Holotype- (CNU VB2005001) (juvenile) skull (20 mm), mandibles, ten cervical vertebrae, cervical ribs, eleven dorsal vertebrae, eighteen dorsal ribs, sternal ribs, eight sacral vertebrae, twenty caudal vertebrae (17.5 mm), chevrons, scapulae (8 mm), coracoids (6 mm), furcula (5 mm), posterolateral sternal processes, humeri (14 mm), radii, ulnae (14 mm), radiale, ulnare, semilunate carpal, metacarpal I, phalanx I-1, metacarpal II (6 mm), phalanx II-1, phalanx II-2, manual ungual II, metacarpal III (6 mm), ilia (8 mm), pubis (8 mm), ischium (4 mm), femora (11 mm), tibiae (16 mm), astragalus, calcaneum, metatarsal I, phalanx I-1, pedal ungual I, metatarsal II, phalanx II-1, phalanx II-2, pedal ungual II, metatarsal III (9 mm), phalanx III-1, phalanx III-2, proximal phalanx III-3, pedal ungual III, metatarsal IV, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV, feather impressions
Reference- Zhang, Hou, Hasegawa, O'Connor, Martin and Chiappe, 2006. The first Mesozoic heterodactyl bird from China. Acta Geologica Sinica. 80(5), 631-635.

Dapingfangornis Li, Duan, Hu, Wang, Cheng and Hou, 2006
D. sentisorhinus Li, Duan, Hu, Wang, Cheng and Hou, 2006
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (LPM 00039) skull (28 mm), sclerotic plates, mandibles, hyoids, cervical vertebrae, dorsal vertebrae, dorsal ribs, sacrum, six caudal vertebrae, pygostyle (15 mm), furcula, sternum (17 mm), scapulae, coracoids (15 mm), humeri (22 mm), radii, ulnae (27 mm), phalanx I-1, manual ungual I, carpometacarpi (11 mm), phalanx II-1, phalanx II-2, manual ungual II, phalanx III-1, ilia, pubes, ischia, femora (23 mm), tibiotarsi (29 mm), fibula, metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsi (16 mm), phalanx II-1, phalanx II-2, pedal ungual II, phalanx III-1, phalanx III-2, phalanx III-3, pedal ungual III, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV, feather impressions
Diagnosis- median nasal horn above antorbital fenestra (?); elongate posterodorsal dentary process; straight lateral coracoid edge; short hypocleidium; articular surfaces for coracoids on sternum at small angle (~100 degrees) to each other; distal expansion of posterolateral sternal process hooked anterolaterally; elongate ulna (>107% of humeral length); extremely slender radius (~30% of ulnar width) (?); elongate metacarpal I (~34-40% of metacarpal II length) (?); metatarsal II trochlea not significantly wider than metatarsal III trochlea (?).
Description- The skull has an odd outline as preserved, but this is due to taphonomy. The dorsal snout is either crushed or missing, making the beak seem more slender than in life. The supposed median nasal horn is suspicious. I wouldn't be surprised if it were the standard maniraptoriform laterally projected lacrimal 'horn', viewed ventrally. This would make sense, because the frontal's concave upper margin would then be the lateral orbital margin in life. What appear to be parietals are preserved posterior to the skull, as seen in the photo of the skeleton (though they aren't illustrated). The ventral margin of the skull is very well preserved, with a maxilla strongly resembling Hebeiornis' and a typical bowed enantiornithine-grade jugal with an expanded anterior end. The 'tympanic' is actually one of the few well preserved enantiornithine-grade quadratojugals. The described 'palatines' are closer in position to pterygoids. The fenestra posteroventral to the 'nasal horn' appears to be a broken or disarticulated space between the frontal and nasal/lacrimal. Two sclerotic plates are apparent, but I don't know what Li et al. identified as a vomer or lacrimal.
The dentaries seem to have an elongate posterodorsal process, which combined with the surangular's outline, indicate a large external mandibular fenestra. I can't identify what Li et al. describe as a prearticular or articular.
The cervical vertebrae are described as heterocoelous, but this could be only partial heterocoely. The presence of at least eight sacral vertebrae indicate an ornithothoracine, while the long pygostyle is characteristic of basal avebrevicaudans.
The furcula is said to have a short hypocleidium, which would be atypical of enantiornithine-grade birds (though known in juveniles and Aberratiodontus). Notably there is no other evidence this is a young individual, as the sternal posterolateral processes are present, the carpometacarpus and tarsometatarsus are fused, and the pygostyle is completely fused. There is a furcula-shaped structure in the illustration, but it's so atypical (one clavicular branch more slender and drawn unfused to the rest; hypocleidium extends posterolaterally; interclavicular angle comparable to basal pygostylians) that either it was drawn exceedingly poorly or not all of it is supposed to be a furcula (or both).
The short sternum with fused distal posterolateral processes indicate an enantiornithine-grade bird. The anterior margin is more acute than most eumaniraptorans, with the exceptions of Longirostravis, Aberratiodontus, Cuspirostrisornis, Yanornis and Ambiortus. The posterolateral processes end in small expansions, as in Jibeinia, Protopteryx, Boluochia, Hebeiornis and Aberratiodontus. However, Dapingfangornis' are apomorphically hooked anterolaterally. The posteromedial processes are very poorly developed, as in Protopteryx, Longipteryx and Hebeiornis (Aberratiodontus lacks them entirely). The posteromedian process is unexpanded, as in Jibeinia, Protopteryx, Longipteryx, Boluochia, Hebeiornis, Eoenantiornis, Sinornis and Aberratiodontus.
The illustration would suggest an ulnar sesamoid and three elongate metacarpals (II-IV), but I ascribe this to the artist instead of the specimen. The radius is drawn as much more slender than most Mesozoic birds, and this could be due to artistic inaccuracy as well. The first metacarpal as illustrated is longer than any other birds except confuciusornithids. Phalanx I-1 is comparable in length to Jibeinia and enantiornithine-grade birds (except Protopteryx, Longipteryx and Eoalulavis). Phalanx II-2 is shorter (compared to II-1) than other coelurosaurs except Jibeinia, Hebeiornis, Sinornis and Eocathayornis. Metacarpal III is illustrated as subequal or barely passing metacarpal II distally, which would be odd for an enantiornithine-grade bird and more like ornithuromorphs and more basal birds. It may be due to inaccurate illustration. Digit III seems to only have one phalanx, though I wouldn't be surprised if a tiny second one were present but not illustrated. This would be unlike Jibeinia and most more basal birds.
Relationships- Li et al. assign Dapingfangornis to the Eoenantiornithiformes because of a short skull, larger nasals and similar sternum. I disagree. The craniofemoral ratio of Dapingfangornis is 1.22, while Eoenantiornis' is 1.32. These are longer than Aberratiodontus (1.07), Hebeiornis (1.05) and Cuspirostrisornis (.99), but comparable to Sinornis (1.22-1.26). Protopteryx (~1.42), Longipteryx (1.90) and Longirostravis (1.80) have longer skulls. Even assuming the nasals are correctly identified in Dapingfangornis, elongate nasals are primitive for birds. The sterna are not very similar, as noted above. Eoenantiornis has a more obtuse anterior margin, large distal expansions on the posterolateral processes (contra Hou et al., 1999), and prominant posteromedial processes. Li et al. distinguish the genera by Dapingfengornis' dubious nasal horn, primitive (and overemphasized by taphonomy) sharp snout, apparently short hypocleidium, and sternal keel (which is unknown in Eoenantiornis because the sternum is in dorsal view; contra Hou et al.,1999).
Reference- Li, Duan, Hu, Wang, Cheng and Hou, 2006. New eoenantiornithid bird from the Early Cretaceous Jiufotang Formation of Western Liaoning, China. Acta Geologica Sinica. 80(1), 38-41.

Elsornis Chiappe, Suzuki, Dyke, Watabe, Tsogtbaatar and Barsbold, 2006
E. keni Chiappe, Suzuki, Dyke, Watabe, Tsogtbaatar and Barsbold, 2006
Late Campanian, Late Cretaceous
Djadokhta Formation, Mongolia
Holotype- (MPD-b 100/201) two posterior cervical vertebrae, two anterior dorsal vertebrae, few dorsal ribs, partial scapulae (63 mm), coracoids (41.7 mm), incomplete furcula, incomplete sternum (>58.55 mm), humeri (77.3 mm), radii (60.65, 60.48 mm), ulnae (66.68 mm), partial carpometacarpi, three pedal phalanges, four pedal unguals, fragments
Diagnosis- (after Chiappe et al., 2006) brachial index (humeral length:ulnar length ratio) substantially greater than 1; scapular shaft with an abrupt bend on its cranial quarter; cranial margin of sternum subdivided in three distinct segments due to widely spaced coracoidal sulci; distal symphysis of the major and minor metacarpals extending for at least one-third the total length of the carpometacarpus.
Reference- Chiappe, Suzuki, Dyke, Watabe, Tsogtbaatar and Barsbold, 2006. A new enantiornthine bird from the Late Cretaceous of the Gobi Desert. Journal of Systematic Palaeontology. 16 pp.

Enantiornithiformes Martin, 1983
Enantiornithidae Nessov and Borkin, 1983
Enantiornis Walker, 1981
E. leali Walker, 1981
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Holotype- (PVL-4035) (~1.0 m) proximal scapula, coracoid (118 mm), proximal humerus
Referred- (PVL-4020) scapula, coracoid, incomplete humerus, radius, partial ulnae, proximal carpometacarpus, manual phalanges (Chiappe, 1996)
(PVL-4023) proximal ulna (Chiappe, 1996)
(PVL-4039) scapula (Walker, 1981)
?(PVL 4049) carpometacarpus (Walker, 1981)
(PVL-4055) scapula (Chiappe, 1996)
(PVL-4181) ulna (Chiappe, 1996)
Diagnosis- distal articulation of metacarpal I shelflike (unknown in other Enantiornithes except Sinornis).
Comments- Walker (1981) named this taxon and based it on PVL-4035, of which only the coracoid was illustrated. The Lecho enantiornithine was described briefly, but the only explicit mention of Enantiornis' characters were several features in a table. Chiappe (1996) described the taxon more fully and listed other specimens as being referred, illustrating the rest of the holotype. Some referred elements were later illustrated by Chiappe and Walker (2002). Walker et al. noted PVL-4049 was also consistant in size with Martinavis? vincei, and the femur PVL-4037, distal tibiotarsus PVL-4033 and partial pelvis PVL-4042 are condistant with both taxa. Many of the other Lecho enantiornithine specimens may belong to Enantiornis, including Soroavisaurus, Lectavis or Yungavolucris.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51 - 53.
Martin, 1983. The origin and early radiation of birds. in Brush and Clark, (eds.).Perspectives in Ornithology. 291-338.
Nessov and Borkin, 1983. New records of bird bones from Cretaceous of Mongolia and Middle Asia. Trudy Zoologicheskogo Instituta AN SSSR. 116, 108–110.
Chiappe, 1996. Early avian evolution in the southern hemisphere: the fossil record of birds in the Mesozoic of Gondwana. Memoirs of the Queensland Museum. 39(3), 533-554.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

Eocathayornis Zhou, 2002
E. walkeri Zhou, 2002
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V10916) premaxilla, maxilla, lacrimal?, jugal?, quadratojugal?, frontal, parietals, quadrate, basicranium?, dentaries, articular, hyoid, six cervical vertebrae, dorsal vertebrae, several partial dorsal ribs, four caudal vertebrae, proximal pygostyle, scapula, coracoids (13.6 mm), sternum (18.5 mm), sternal ribs, humeri (23.5 mm), radii (25.6 mm), ulnae (26 mm), radiale, ulnare, carpometacarpus (14 mm), phalanx I-1 (6 mm), manual ungual I (2.1 mm), phalanx II-1 (7 mm), phalanx II-2 (4.3 mm), manual ungual II (2.4 mm), phalanx III-1 (2.5 mm), manual ungual III (1.3 mm)
Comments- Collected in 1994, Martin and Zhou (1997) first referred this specimen to Cathayornis.
References- Martin and Zhou, 1997. Archaeopteryx-like skull in Enantiornithine bird. Nature. 389, 556.
Zhou, 2002. A new and primitive enantiornithine bird from the Early Cretaceous of China. Journal of Vertebrate Paleontology. 22(1), 49-57.

Eoenantiornithiformes Hou, Martin, Zhou and Feduccia, 1999
Eoenantiornithidae Hou, Martin, Zhou and Feduccia, 1999
Eoenantiornis Hou, Martin, Zhou and Feduccia, 1999
E. buhleri Hou, Martin, Zhou and Feduccia, 1999
Late Barremian-Early Aptian, Early Cretaceous
Jianshangou Beds of Yixian Formation, Liaoning, China
Holotype- (IVPP V11537) (135 mm) incomplete skull (22 mm), mandibles, hyoid, eleven cervical vertebrae (~29 mm), dorsal vertebrae, several dorsal ribs, two uncinate processes, gastralia, anterior sacrum, several caudal vertebrae, distal pygostyle, scapula, coracoids (12.5 mm), furcula, sternum, humerus (29.5 mm), partial radii, incomplete ulnae (31 mm), radiale?, ulnares, carpometacarpi (12 mm), phalanx I-1, manual ungual I, phalanx II-1, phalanx II-2, manual ungual II, phalanx III-1, partial ilium, distal pubes, distal ischium, incomplete femur (26.5 mm), tibiotarsus (31 mm), metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsus (22.3 mm), phalanx II-1, phalanx II-2, pedal ungual II, phalanx III-1, feather impressions
References- Hou, Martin, Zhou and Feduccia, 1999. Archaeopteryx to opposite birds - missing link from the Mesozoic of China. Vertebrata PalAsiatica. 37(2), 88–95.
Zhou, Chiappe and Zhang, 2005. Anatomy of the Early Cretaceous bird Eoenantiornis buhleri (Aves: Enantiornithes) from China. Canadian Journal of Earth Sciences. 42, 1331–1338.

"Gobipipus" Mourer-Chauvire, 1995
"G. reshetovi" Mourer-Chauvire, 1995
Late Campanian, Late Cretaceous
Baruungoyot Formation, Mongolia
Material- (PIN 4492-3) (embryo) premaxilla, basisphenoid, dentary, presacral vertebrae, scapulae, coracoid, humeri, radii, ulna, metacarpal II, phalanx II-1, metacarpal III (Kurochkin, 2000)
(PIN coll.) (Kurochkin, 1996)
(ZPAL MgR-I/33) (embryo) (skull ~20 mm) premaxillae, maxilla, nasals, frontal, squamosal, quadrate, ectethmoid, exoccipital, basioccipital, posterior mandibular fragment, atlas(?), anterior cervical neural arch, eighth cervical neural arch, ninth cervical neural arch, fragmentary tenth cervical neural arch, several cervical centra, eleventh dorsal neural arch, twelfth dorsal neural arch, first dorsal neural arch, second dorsal neural arch, third dorsal neural arch, fourth dorsal neural arch, fifth dorsal neural arch, sixth dorsal neural arch, seventh dorsal neural arch, four dorsal rib fragments, scapulae (11 mm), coracoid fragments, incomplete humeri (14 mm), incomplete radius (15.9 mm), incomplete ulna (16.1 mm), metacarpal II, metacarpal III (7.5 mm), distal femur, proximal tibia, pedal phalanx, pedal ungual, eggshells (Elzanowski, 1981)
(ZPAL MgR-I/34) (embryo) quadrate fragment, pterygoid fragment, parabasisphenoid, braincase fragments, mandibular fragment, atlas, axis, third cervical vertebra, fourth cervical vertebra (1.3 mm), fifth cervical vertebra (1.3 mm), sixth cervical vertebra, seventh cervical vertebra (1.7 mm), eighth cervical vertebra (1.7 mm), ninth cervical vertebra, tenth cervical vertebra, eleventh cervical vertebra, twelfth cervical vertebra (1.3 mm), first dorsal vertebra (1.3 mm), second dorsal vertebra (1.6 mm), third dorsal neural arch fragment, five anterior dorsal ribs, incomplete scapulae, coracoids, partial furcula, proximal humeri (~18.7 mm), distal radius, distal ulna, ulnare, distal carpals, phalanx I-1 (~2.6 mm), manual ungual I (~1.3 mm), metacarpal II (11.1 mm), metacarpal III (11.8 mm), eggshells (Elzanowski, 1981)
(ZPAL MgR-I/88) (embryo) (skull ~88 mm) premaxillae, maxillae, nasal, frontal, ectethmoid, anterior mandibles, penultimate pedal phalanx (3.6 mm), pedal ungual (3.3 mm), eggshells (Elzanowski, 1981)
(ZPAL MgR-I/89) (embryo) three dorsal neural arches, fragmentary humerus(?), fragmentary radius(?), fragmentary ulna(?), metacarpal II, metacarpal III, eggshells (Elzanowski, 1981)
(ZPAL MgR-I/90) (embryo) fragmentary tibia(?), pedal ungual, eggshells (Elzanowski, 1981)
(ZPAL MgR-I/91) (embryo) posterior skull fragment, fragmentary humerus, fragmentary radius, fragmentary ulna, fragmentary metacarpal II, fragmentary metacarpal III, eggshells (Elzanowski, 1981)
(ZPAL MgR-I/92) (embryo) fragmentary coracoid(?), fragmentary humerus(?), fragmentary metacarpal II, two pedal phalanges, eggshells (Elzanowski, 1981)
Comments- Several embryos were described by Elzanowski (1981), tentatively referred to Gobipteryx minuta because of several cranial features. Martin (1983, 1995) and Elzanowski (1995) followed this assignment. Chatterjee and Kurochkin (1994) and Kurochkin (1995, 1996) separated ZPAL MgR-I/33 and two new specimens in the PIN collections from ZPAL MgR-I/34 as a new taxon of palaeognath. This was to be described in Nature by Chatterjee, Kurochkin and Mikhailov as "Gobipipus reshetovi" (Mourer-Chauvire, 1995). Indeed, such a reference is cited as a manuscript by Kurochkin (1996) and Starck and Ricklefs (1998) and "in press" in Nature by Kurochkin (1995). It has not been published. The name "Gobipipus reshetovi" was published by Mourer-Chauvire (1995) and later by Chatterjee (1997), though only as nomina nuda. Ford (www.paleofile.com) lists "Gobipipus elzanowskii" as a nomen nudum ascribed to Chatterjee in 1994, though the 'Chatterjee, 1994' entry in his bibliography is a miscitation of Chatterjee and Kurochkin, 1994. That species name has not been published to my knowledge. By 2000, Kurochkin (2000, 2004) no longer believed the PIN specimens and ZPAL-MgR-I/33 were a separate taxon from the enantiornithine specimens. The differences were ascribed to ontogeny. Kurochkin (2000, 2004) felt these embryos were a new taxon of enantiornithine which could be distinguished from Gobipteryx based on several characteristics. As Kurochkin currently has the specimens and manuscript, the possibility of "Gobipipus reshetovi" being published as a new taxon of paleognath seems slim.
The eggs have been named Gobioolithus minor and are laevisoolithid (Mikhailov, 1996).
The specimens are enantiornithine because they exhibit the following characters- deep fossa in dorsal surface of coracoid (ZPAL MgR-I/34; also in Apsaravis); well-developed fossa on midline of proximal humerus making articular surface appear V-shaped in proximal view (ZPAL MgR-I/34); deltopectoral crest projected dorsally (ZPAL MgR-I/34; (also in Confuciusornis, Ambiortus, Apsaravis, Gansus and Ichthyornis); metacarpal III extends distally past metacarpal II (ZPAL MgR-I/34; also in some Shenzhouraptor specimens); scapular acromion much wider than deep (ZPAL MgR-I/34; also in Ambiortus and Apsaravis); scapulocoracoid articulation with coracoid process and scapular cotyla (ZPAL MgR-I/34).
References- Elzanowski, 1981. Embryonic bird skeletons from the Late Cretaceous of Mongolia. Palaeontologica Polonica. 42, 147-176.
Martin, 1983. The origin and early radiation of birds. in Brush and Clark, (eds.).Perspectives in Ornithology. 291-338.
Chatterjee and Kurochkin, 1994. An new embryonic bird from the Cretaceous of Mongolia. Journal of Vertebrate Paleontology. 14(3), 20A.
Elzanowski, 1995. Cretaceous birds and avian phylogeny. Cour. Forschungsinst. Senckenb. 181, 37-53.
Kurochkin, 1995. Synopsis of Mesozoic birds and early evolution of Class Aves. Archaeopteryx. 13, 47-66.
Martin, 1995. The enantiornithines: terrestrial birds of the Cretaceous. Courier Forschungsinstitut Senckenberg. 181, 23–36.
Mourer-Chauviré, 1995. Society of Avian Paleontology and Evolution. Information Newsletter.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.
Mikhailov, 1996. The eggs of birds in the Upper Cretaceous of Mongolia. Paleontologichesky Zhurnal. 1, 19-121. [in Russian]
Chatterjee, 1997. The Rise of Birds. 312 pp.
Starck and Ricklefs, 1998. Patterns of development: The altricial-precocial spectrum. in Starck and Ricklefs (eds.). Avian Growth and Development. Evolution within the altricial precocial spectrum. University Press, New York. pp 3-30.
Kurochkin, 2000. Mesozoic birds of Mongolia and the former USSR. in Benton et al., eds. The Age of Dinosaurs in Russia and Mongolia. 533-559.
Kurochkin, 2004. The truth about Gobipteryx. Sixth International Meeting of the Society of Avian Paleontology and Evolution. Abstracts. 33-34.
Chatterjee, Kurochkin and Mikhailov, MS. Embryonic bird skeletons from the Cretaceous of Mongolia.

Gobipterygiformes Elzanowski, 1974
Gobipterygidae Elzanowski, 1974
Gobipteryx Elzanowski, 1974
G. minuta Elzanowski, 1974
= Nanantius valifanovi Kurochkin, 1997
Late Campanian, Late Cretaceous
Baruungoyot Formation, Mongolia
Holotype- (ZPAL MgR-I/12) (~190 mm) premaxillae, quadrate, vomeral fragment(?), palatine, partial ectopterygoid, partial pterygoids, mandibles (38 mm), cervical vertebral fragments
Referred- ?(PIN 4492-1; holotype of Nanantius valifanovi) (~175 mm) anterior premaxillae, frontals, pterygoids, parabasisphenoid, anterior dentaries, axis (6.2 mm), seven incomplete cervical vertebrae (5.2 mm), incomplete anterior dorsal vertebra, sacrum (15 mm), four caudal vertebrae, pygostyle (8.6 mm), proximal scapula, partial coracoids (~30.8 mm), partial furcula, incomplete humeri (~44 mm), incomplete radius (~43 mm), incomplete ulnae (~57 mm), distal metacarpal II, phalanx II-1 (11.3 mm), distal metatarsal III, phalanx III-1 (4.3 mm), partial ilia, distal pubes, partial femur (~36 mm), femoral fragment, incomplete tibiotarsus (~59.9 mm), tibiotarsal fragments, incomplete fibulae, metatarsal I (4.1 mm), proximal phalanx I-1, pedal ungual I (8 mm), incomplete tarsometatarsi (metatarsal II 24.1 mm, metatarsal III 25 mm, metatarsal IV 23.7 mm), proximal phalanx II-1, phalanx II-2, pedal ungual II (8.5 mm), phalanx III-1, proximal phalanx III-2, distal phalanx III-3, pedal ungual III (7.8 mm), pedal digit IV phalanges, pedal ungual IV (7.6 mm), thirty eggshell fragments (Kurochkin, 1996)
(ZPAL MgR-I/32) premaxillae, maxillae, nasal fragment, partial vomer, palatine, partial pterygoids, dentaries, surangular, angular (Elzanowski, 1976)
Late Campanian, Late Cretaceous
Djadokhta Formation, Mongolia
?(IGM 100/1011) premaxillae, maxillae, partial nasals, vomer, palatines, pterygoid, ectethmoid, nine sclerotic ossicles, anterior dentary (Chiappe, Norell and Clark, 2001)
Comments- While Chiappe et al. (2001) synonymized Nanantius valifanovi with Gobipteryx minuta, Kurochkin (2004) kept them separate and referred IGM 100/1011 to a new species of Nanantius instead of G. minuta. This was based on an unpublished character analysis, with only a few supposedly distinguishing characters listed. N. valifanovi was said to differ from Gobipteryx in the thin and sharp tomium, dorsal premaxillary groove, and absence of a ventral symphyseal crest on the dentary.
The eggshells associated with PIN 4492-1 have been assigned to the oogenus Subtilioolithus in the Laevisoolithidae by Mikhailov (1996).
References- Elzanowski, 1974. Preliminary note on the palaeonathous birds from the Upper Cretaceous of Mongolia. Results of the Polish-Mongolian Paleontological Expeditions - Part V. Palaeontologica Polonica. 30, 103-109.
Elzanowski, 1976. Palaeognathous bird from the Cretaceous of Central Asia. Nature. 264, 51-53.
Elzanowski, 1977. Skulls of Gobipteryx (Aves) from the Upper Cretaceous of Mongolia. Results of the Polish-Mongolian Paleontological Expeditions - Part VII. Palaeontologica Polonica. 37, 153-165.
Elzanowski, 1981. Embryonic bird skeletons from the Late Cretaceous of Mongolia. Palaeontologica Polonica. 42, 147-176.
Elzanowski, 1995. Cretaceous birds and avian phylogeny. Cour. Forschungsinst. Senckenb. 181, 37-53.
Kurochkin, 1996. A new Enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue: 50pp.
Mikhailov, 1996. The eggs of birds in the Upper Cretaceous of Mongolia. Paleontologichesky Zhurnal. 1, 19-121. [in Russian]
Chiappe, Norell and Clark, 2001. A new skull of Gobipteryx minuta (Aves: Enantiornithes) from the Cretaceous of the Gobi Desert. American Museum Novitates. 3346, 1-15.
Kurochkin, 2004. The truth about Gobipteryx. Sixth International Meeting of the Society of Avian Paleontology and Evolution. Abstracts. 33-34.

Hebeiornis Yan vide Xu, Yang and Deng, 1999
= Vescornis Zhang, Ericson and Zhou, 2004
H. fengningensis Yan vide Xu, Yang and Deng, 1999
= Vescornis hebeiensis Zhang, Ericson and Zhou, 2004
Early Aptian, Early Cretaceous
Qiaotou Member of the Huajiying Formation, Hebei, China
Holotype- (NIGP 130722) (125 mm; subadult) skull, mandibles, hyoid, atlas, axis, third cervical vertebra, fourth cervical vertebra, fifth cervical vertebra, sixth cervical vertebra, seventh cervical vertebra, eighth cervical vertebra, ninth cervical vertebra, several dorsal vertebrae, dorsal ribs, gastralia, sacrum, pygostyle, scapulae (13 mm), coracoids, furcula, sternum, sternal ribs, humeri (25 mm), radii, ulnae (30 mm), radiales, ulnares, metacarpal I, phalanx I-1, manual ungual I, carpometacarpus, phalanx II-1, phalanx II-2, manual ungual II, phalanx III-1, partial ilium, partial pubes, incomplete ischium, femora (25 mm), tibiotarsi (30 mm), proximal tarsals, metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsi (18 mm), phalanx II-1, phalanx II-2, pedal ungual II, phalanx III-1, phalanx III-2, phalanx III-3, pedal ungual III, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV
Comments- Jin et al. (2008) reassign Hebeiornis' horizon to the Qiaotou Member of the Huajiying Formation, as opposed to the Yixian Formation which was stated in Xu et al. (1999) and Zhang et al. (2004).
Hebeiornis is listed as gen. et sp. nov. in Xu et al. (1999) and attributed to Yan, 1999, which I assume to mean they are the only author (perhaps a mispelling of Yang You-shi?) taking credit for the name, as opposed to there being a separate Yan, 1999 publication. The photograph in Xu et al. is extremely poor, and only labeled "Bird fossils in the bottom of the Jurassic Yixian Formation". However, only one Yixian bird specimen is described in the paper, and the pose described for Hebeiornis is the same (complete specimen exposed ventrally, neck curving to its left). This is obviously a photograph of the holotype of Vescornis hebeiensis. The latter taxon was also thought to be from the Yixian Formation of Senjitsu in Fengning County, though that horizon has recently been changed (see above). The measurements match fairly well with Vescornis (skull ~24 vs. 27 mm; scapula ~17 vs. 13 mm; humerus ~24 vs. 25 mm; ulna ~25 vs. 30 mm; femur ~24 vs. 25 mm; tibia ~30 vs. 30 mm), as do the few osteological details with the exception of the pygostyle. As Babelfish translates, Hebeiornis "does not have the tail synthesis bone", while Vescornis has a pygostyle. Then again, the authors were apparently unfamiliar with the numerous basal pygostylians with elongate pygostyles (with the exception of Cathayornis, which they never discuss, only list), perhaps Vescornis' elongate pygostyle was too dissimilar to ornithurine sensu stricto pygostyles for them to count it? Or perhaps it's just another failing of a poor description or translation. So accepting the two names are based on the same specimen, Hebeiornis clearly has chronological priority by five years and appears to have a valid description, albeit very poorly written. Jin et al. (2008) confirm they are the same specimen, though they regard Hebeiornis as a nomen nudum.
References- Xu, Yang and Deng, 1999. First discovery of Mesozoic bird fossils in Hebei Province and its significance. Regional Geology of China. 18(4), 444-448.
Zhang, Ericson and Zhou, 2004. Description of a new enantiornithine bird from the Early Cretaceous of Hebei, northern China. Canadian Journal of Earth Sciences. 41(9), 1097-1107.
Jin, Zhang, Li, Zhang, Li and Zhou, 2008. On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota. Chinese Science Bulletin. 53(18), 2820-2827.

Jibeinia Hou, 2000
= "Jibeinia" Hou, 1997
J. luanhera Hou, 2000
= "Jibeinia luanhera" Hou, 1997
Early Aptian, Early Cretaceous
Qiaotou Member of the Huajiying Formation, Hebei, China
Holotype- (IVPP collection; lost) (juvenile) partial skull, mandible (22 mm), six cervical vertebrae (~2.4 mm), five dorsal vertebrae (~2.9 m), dorsal ribs, gastralia, sacrum, six caudal vertebrae, pygostyle (13 mm), scapula (20 mm), coracoids (11.5 mm), incomplete furcula, sternum (17 mm), humerus (23.3 mm), radius (24.2 mm), ulna (24 mm), semilunate carpal, ulnare, metacarpal I (2 mm), phalanx I-1 (4 mm), manual ungual I (2.5 mm), metacarpal II (9.3 mm), phalanx II-1 (6 mm), phalanx II-2 (3.7 mm), manual ungual II (2.1 mm), metacarpal III (8.3 mm), phalanx III-1 (1.5 mm), phalanx III-2 (2.9 mm), manual ungual III (1 mm), partial ilium, pubis (21 mm), partial ischium, femora (22.2 mm), tibiae (28 mm), astragali, calcanea, distal tarsal, metatarsal I, phalanx I-1, pedal ungual I, metatarsal II, phalanx II-1, phalanx II-2, pedal ungual II, metatarsal III (16.3 mm), phalanx III-1, phalanx III-2, proximal phalanx III-3, pedal ungual III, metatarsal IV, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV, feather impressions
Diagnosis- narrow furcular branches; metacarpal II does not extend past metacarpal II (?); three phalanges on manual digit III (?); trochlea of metatarsal II not wider than that of metatarsal III (?).
Other diagnoses- Of the diagnostic characters listed by Hou (1997), most are symplesiomorphic for enantiornithines (numerous unserrated maxillary teeth; large, broad sternum; reduced manual digit III; fused pubic symphysis; metatarsals partially fused proximally and unfused distally; metatarsal II shorter than metatarsal III or IV) or ambiguous (extremely concave cervical centra; unexpanded distal pubes). The narrow posteromedian sternal process is present in almost all enantiornithines as derived as Longipteryx, while the final character (poorly developed posterolateral sternal processes) is problematic. The distal end of the right process is covered by another element, while the right process has a broader base which may be the remains of a large distal expansion. If the right side is more accurate, it would resemble Hebeiornis, while the left side could resemble Eoenantiornis. Another possibility is that the sternum is similar to Sinornis in possessing a small anterolateral process on the right side, with most of the posterolateral process broken off. Interestingly, if manual phalanx III-1 is actually a broken piece of metacarpal III, both the apparently short metacarpal III and presence of three phalanges on that digit would be resolved and the manus would resemble those of other enantiornithines. Hou previously claims Confuciusornis has five phalanges on manual digit III in the same book (again probably due to a broken element), so such a mistake by him would not be unheard of. It would still have two phalanges on the digit however, which would be like basal enantiornithines but unlike some derived taxa.
Comments- The name "Jibeinia luanhera" was first used in Hou (1997), but only in the captions of three illustrations. In the text, it was merely called Ji Bei bird (this is untrue in the English translation). Because the scientific name was not given in the text itself, "Jibeinia" was a nomen nudum. Later, Hou (2000) used the scientific name in the text of his semipopular Picture Book of Chinese Fossil Birds, with accompanying illustrations and disgnosis. This counts as the first official use of the name. Unfortunately, neither work contains trustworthy descriptions or accurate illustrations. The illustrations in Hou (1997) are hopelessly schematic, while the skeletal reconstructions in Hou (2000) aren't respresentative of bird anatomy, let alone that of Jibeinia itself. Hou's (1997) descriptions contain features not known in birds (e.g. septomaxillae, presternae) as well as numerous characters which clash with those described in more recent and better illustrated papers (e.g. Confuciusornis in Chiappe et al., 1999). In addition, the holotype is presently lost (Hou pers. comm., 2001 to Zhang et al., 2004) and existing casts are of low quality. Thus all morphological details of Jibeinia are suspect, except the few which can be gleaned from published photographs.
Jin et al. (2008) reassign Jibeinia's horizon to the Qiaotou Member of the Huajiying Formation, as opposed to the Yixian Formation which was stated in Hou (1997) and Zhang et al. (2004).
Based on comparison with undoubted juvenile enantiornithines (Dalingheornis, Liaoxiornis, GMV 2158, GMV 2159, etc.), Jibeinia is near certainly a juvenile as well. Characters supporting this conclusion include- unfused sacrum; sternal keel absent; high interclavicular angle; humeral head not concave proximally; humeral distal condyles undeveloped, which in turn causes the ventral condyle to not project distally; carpometacarpus fusion absent; pelvic fusion absent; cnemial crest absent; tibiotarsal, proximal tarsal and distal tarsal fusion absent. Some of these characters are seen in most of the taxa described by Hou (1997), so may be due to the schematic illustration quality or incorrect description instead.
Jibeinia exhibits several primitive characters for an ornithothoracine. It supposedly lacks a sternal keel, has three phalanges on manual digit III, and a metacarpal I which is unfused to the carpometacarpus. In addition, the unfused carpometacarpus and pelvis, absent cnemial crest and unfused tibiotarsus and tarsus are all near certainly juvenile characters, being more primitive than more basal avebrevicaudans like Sapeornis and Confuciusornis. However, Jibeinia exhibits a narrower interclavicular angle (~66 degrees) and less phalanges on manual digit III than confuciusornithids and most more basal maniraptorans. Because Jibeinia is probably a juvenile, it is unclear if some characters it possesses are due to being juvenile or being basal. The posteromedian sternal process is narrow as in enantiornithines, but the ventral humeral condyle doesn't appear to be distally projected, if the illustration can be trusted. The latter is the juvenile condition for enantiornithines, however. Metatarsal IV is reduced in width as in enantiornithines.
Zhang et al. (2004) suggested Jibeinia may be a senior synonym of Hebeiornis (described by those authors as Vescornis), which they described from the same formation. This was based on their identical size and numerous similar characteristics. Besides those characters listed in the diagnosis, Jibeinia differs from Hebeiornis in- more shallow anterior dentary; elongate posteromedial sternal processes; narrow ventral tubercle of humerus; larger manual ungual I. Jibeinia supposedly has amphicoelous cervicals and dorsals, while Hebeiornis has heterocoelous cervicals and an opisthocoelous dorsal (but note the comment above regarding enantiornithine central articulations). Besides the numerous juvenile characters listed above (some of which Hebeiornis shows as well- unfused sacrum, metacarpal I unfused to carpometacarpus, proximal tarsals unfused to tibia), Jibeinia is younger based on supposed foramina between neural arches in the pygostyle, and its undeveloped distal femoral condyles. Based on comparison to Hebeiornis, the proximal coracoid of Jibeinia may be broken off, though Hou does describe it as having a rounded head. If it is complete, it is shorter than in Hebeiornis.
References- Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Hou, 2000. Picture Book of Chinese Fossil Birds. Yunnan Science and Technology Press, Kunming, China.
Zhang, Ericson and Zhou, 2004. Description of a new enantiornithine bird from the Early Cretaceous of Hebei, northern China. Canadian Journal of Earth Sciences. 41(9), 1097-1107.
Jin, Zhang, Li, Zhang, Li and Zhou, 2008. On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota. Chinese Science Bulletin. 53(18), 2820-2827.

Largirostrornis Hou, 1997
L. sexdentoris Hou, 1997
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (IVPP V10531) (~160 mm) skull (32 mm), partial mandibles, cervical vertebrae, several dorsal vertebrae, gastralia, sacrum, caudal vertebrae, coracoids (19 mm), partial furcula, sternum (~22 mm), humerus (31 mm), radius, ulna (~31.5 mm), carpometacarpus (15 mm), manual ungual (2 mm), ilia, pubes, ischia, femora (28.5 mm), tibiotarsi (33 mm), fibula, tarsometatarsi (19 mm), pedal phalanges, pedal unguals
Reference- Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.

Liaoxiornithiformes Hou, Zhou, Zhang and Gu, 2002
Liaoxiornithidae Hou, Zhou, Zhang and Gu, 2002
Liaoxiornis Hou and Chen, 1999
= Lingyuanornis Ji and Ji, 1999
L. delicatus Hou and Chen, 1999
= Lingyuanornis parvus Ji and Ji, 1999
Early Aptian, Early Cretaceous
Dawangzhangzi Beds of Yixian Formation, Liaoning, China
Holotype- (IVPP V 130723, GMV2156 is counterpart and holotype of Lingyuanornis parvus) (82 mm; juvenile) skull (20.3 mm), mandible (20 mm), ten cervical vertebrae, cervical rib, eleven dorsal vertebrae, twenty-two dorsal ribs, sacrum (11 mm), seven caudal vertebrae (4.1 mm), pygostyle (16 mm), scapulae (10.1, 10.1 mm), coracoids (7.5 mm), furcula (7.6 mm), sternum (3.2 mm), humeri (15.5, 15.4 mm), radii (14.9 mm), ulnae (15.6 mm), radiale, ulnare, semilunate carpal, metacarpal I, metacarpal II, manual phalanx II-1 (4.3 mm), metacarpal III (7.4 mm), phalanx III-1, ilia (9-10 mm), pubes (6.6 mm), femora (14.4, 14.5 mm), tibiae (16.5, 17.1 mm), tarsal, metatarsal I, phalanx I-1, pedal ungual I, metatarsal II (9.6 mm), metatarsal III (10.4 mm), metatarsal IV (9.6 mm), pedal phalanges, feather impressions
References- Hou and Chen, 1999. Liaoxiornis delicatus gen. et sp. nov., the smallest Mesozoic bird. Chinese Science Bulletin. 44(9): 834-838.
Ji and Ji, 1999. A new genus of the Mesozoic birds from Lingyuan, Liaoning, China. Chinese Geology. 262, 45-48.
Chiappe and Ji, 2002. Enantiornithine (Aves) neonates from the Early Cretaceous of China. Journal of Vertebrate Paleontology. 22(3), 43A.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Hou, Zhou, Zhang and Gu, 2002. Mesozoic birds from western Liaoning in China. ISBN 7-5381-3392-5. 120 pp.

Martinavis Walker, Buffetaut and Dyke, 2007
Other diagnoses- Walker et al. note numerous additional characters which they correctly state are shared with other enantiornithines- proximal margin of humerus concave in its central portion, rising both ventrally and dorsally on either side; bicipital crest prominent; ventral surface of bicipital crest bearing a small fossa for muscle attachment; proximally L-shaped humeral head; well-marked depression underneath the proximal head of the humerus; weakly developed distal condyles; flat distal end that is not deflected dorsally. The pneumotricipital fossa is no wider in M? vincei than Enantiornis, Gurilynia, Halimornis or Otogornis, and is narrow in M. cruzyensis. The lack of a perforated ventral tubercle is plesiomorphic and also present in such taxa as Halimornis and Eoalulavis. Most enantiornithine deltopectoral crests could be described as "flat and broad", while the stated lack of ventral curvature is difficult to evaulate. The lack of a marked distal angle between the deltopectoral crest and shaft distally is primitive and also seen in such taxa as Eoalulavis, Eocathayornis, Hebeiornis, Otogornis, Pengornis and Sinornis. The bicipital crest is no smaller than in Gurilynia. It is indeed more anteriorly angled in supposed M. sp. specimen KU-NM-37 (but not in supposed M. sp. PVL-4025) than Enantiornis, Halimornis or Gurilynia, but is less angled than Elsornis. "Ventral margin of bicipital crest small" is a confusing statement, and the ventrally placed bicipital fossa is also present in Gurilynia and Halimornis while that of M. cruzyensis is anteroventrally placed. The ventral condyle is as poorly developed in Elsornis, Eocathayornis, Kizylkumavis and Sinornis. Alexornis, Elsornis, Kizylkumavis and Otogornis lack both scapulotricipital and humerotricipital grooves as well. The ventral epicondyle is as large and distally projected in Kizylkumavis and probably Alexornis. A transversely oriented dorsal condyle is present in almost all enantiornithines. Walker et al. also included a differential diagnosis, though it repeats some characters of the general diagnosis (anteriorly angled bicipital crest; deltopectoral crest smoothly angled; transversely oriented dorsal condyle) and has another which contradicts the general diagnosis (small entepicondyle). Of the remaining characters, the shaft is actually less gracile than Enantiornis (and most other enantiornithines), not more. A laterally positioned ectepicondyle is present in all enantiornithines.
Comments- Walker et al. established this genus for several large humeri from the Late Cretaceous of Argentina (M. vincei, PVL-4025, 4028 and 4046), France (M. cruzyensis) and the US (KU-NM-37). However, as seen above, none of these specimens share unique apomorphies. In fact, M. cruzyensis lacks two of the supposed Martinavis synapomorphies while PVL-4025 lacks four. This makes referral of any specimens besides the cruzyensis holotype to Martinavis problematic.
Reference- Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.
M. cruzyensis Walker, Buffetaut and Dyke, 2007
Late Campanian-Early Maastrichtian, Late Cretaceous
Massecaps, Herault, France
Holotype- (ACAP-M 1957) humerus (92 mm)
Other diagnoses- Several characters in Walker et al.'s diagnosis are identical to those for their Martinavis generic diagnosis and are present in other taxa as noted above- bicipital crest of humerus strongly projected anteriorly; broad deltopectoral crest; lack of a perforated ventral tubercle; ventral epicondyle enlarged and extended distally. Of the remaining characters, the capital groove is also wide in Gurilynia and Eoalulavis and is also deep in most enantiornithines (except Elsornis; it is actually said to be deeper in M? vincei). The deltopectoral crest is also deeply concave posteriorly in M? vincei and Halimornis. The dorsal and ventral condyles are not enlarged or expanded more than M? vincei, Gurilynia, Kizylkumavis or Alexornis.
Reference- Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

Martinavis? vincei Walker, Buffetaut and Dyke, 2007
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Holotype- (PVL-4054) humerus (110 mm)
Paratype- (PVL-4059) distal humerus (~110 mm)
Referred- ?(PVL-4266) proximal humerus (Chiappe, 1996)
Other diagnoses- The bicipital crest was said to be angled more anteriorly than in M. cruzyensis, but is even more anteriorly angled in Elsornis. The capital groove seem equally deep in Enantiornis and probably Eocathayornis. Finally, the distal condyles do not appear "more distally enlarged" than in M. cruzyensis.
Comments- PVL-4054 was first illustrated by Walker (1981) and later by Chiappe and Walker (2002) as Enantiornithes, and described as the holotype of Martinavis vincei by Walker et al. (2007). Chiappe (1996) listed PVL-4059 as Enantiornithines and it was later made the paratype of M. vincei. However, as noted the the Other diagnoses of Martinavis, none of Walker et al.'s supposed apomorphies for that genus are valid. This makes referring any vincei to it problematic and indeed it resembles Gurilynia and Halimornis more than Martinavis in having a broad pneumotricipital fossa and ventrally placed bicipital fossa. PVL-4266 is a proximal humerus photographed by Chiappe (1996) which appears to be nearly identical to PVL-4054 in outline and may therefore belong to the same taxon, though it was not mentioned by Walker et al.. They both appear to be a different taxon than Enantiornis, PVL-4022, PVL-4025 or PVL-4043, and may belong to Lectavis, Yungavolucris or Soroavisaurus.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Chiappe, 1996. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. Munchner Geowissenschaftliche Abhandlungen (A). 30, 203–244.
Chiappe and Walker, 2002. Skeletal morphology and systematics of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer (eds.). Mesozoic Birds - Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

Nanantius Molnar, 1986
Diagnosis- (after Kurochkin and Molnar, 1997) laterally convex tibiotarsal shaft; caudal intercotylar prominence on the proximal tibiotarsal articular surface; well expressed fibular crest on lateral edge of tibial shaft; oblong fossae on cranial and caudal sides of the fibular crest.
Comments- The partial skeleton PIN 4492-1 was originally described as a new species, Nanantius valifanovi (Kurochkin, 1996), but has been identified as a specimen of Gobipteryx minuta (Chiappe et al., 2001). This limits known Nanantius specimens to partial tibiotarsi and a vertebra from the Tollebuc Formation of Queensland.
References- Molnar, 1986. An enantiornithine bird from the Lower Cretaceous of Queensland, Australia. Nature 322 736-738.
Kurochkin, 1996. A new Enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue: 50pp.
Kurochkin and Molnar, 1997. New material of enantiornithine birds from the Early Cretaceous of Australia. Alcheringa 21:291-297.
Chiappe, Norell and Clark. 2001. A new skull of Gobipteryx minuta (Aves: Enantiornithes) from the Cretaceous of the Gobi Desert. American Museum Novitates 3346: 1-15.
N. eos Molnar, 1986
Albian, Early Cretaceous
Toolebuc Formation, Queensland, Australia
Holotype- (QM F12992) (~135 mm) incomplete tibiotarsus (~34 mm)
Referred- ....(QM F12991) cervical vertebra (Kurochkin and Molnar, 1997)
(QM F16811) proximal tibiotarsus (Kear et al., 2003)
Diagnosis- (modified from Kurochkin and Molnar, 1997) lateral cnemial crest absent; absence of long, low lateral eminence in fossa lateral to lateral cnemial crest; cranial cnemial crest on the medial edge of the tibiotarsus; nutrient foramen on caudal side of shaft near termination of fibular crest.
Comments- The cervical vertebra (QM F12991) was found less than 5 cm from the holotype tibiotarsus, so may belong to the same individual and taxon. The proximal tibiotarsus described by Kear et al. (2003) from ichthyosaur gut contents is more similar to N. eos than QM F31813 in the absence of a lateral cnemial crest and eminence lateral to that. It is provisionally assigned to N. eos here based on provenence.
References- Molnar, 1986. An enantiornithine bird from the Lower Cretaceous of Queensland, Australia. Nature 322 736-738.
Kurochkin and Molnar, 1997. New material of enantiornithine birds from the Early Cretaceous of Australia. Alcheringa 21:291-297.
Kear, Boles and Smith, 2003. Unusual gut contents in a Cretaceous ichthyosaur. Proc. Roy. Soc. London B (Suppl).
N. sp. nov. (Kurochkin and Molnar, 1997)
Albian, Early Cretaceous
Toolebuc Formation, Queensland, Australia
Material- (QM F31813) proximal tibiotarsus (~28 mm)
Diagnosis- (modified from Kurochkin and Molnar, 1997) lateral cnemial crest present; long, low lateral eminence in fossa lateral to lateral cnemial crest; cranial cnemial crest caudal to the medial edge of the tibiotarsus; nutrient foramen on caudal side of shaft near termination of fibular crest absent.
Reference- Kurochkin and Molnar, 1997. New material of enantiornithine birds from the Early Cretaceous of Australia. Alcheringa 21:291-297.

Neuquenornis Chiappe and Calvo, 1994
N. volans Chiappe and Calvo, 1994
Santonian, Late Cretaceous
Bajo de le Carpa Formation of the Rio Colorado Subgroup, Argentina
Holotype- (MUCPv-142) (~290 mm) posterior skull, five partial dorsal vertebrae, incomplete scapula, coracoids (33.4 mm), furcula, incomplete sternum, sternal ribs, incomplete humeri, incomplete radii (70.5 mm), incomplete ulnae (72.1 mm), ulnare, carpometacarpus, proximal phalanx II-1, pelvic(?) fragment, incomplete femur, partial tibiotarsi (~87.7 mm), metatarsal I (8.3 mm), phalanx I-1 (10.7 mm), pedal ungual I (14.6 mm), incomplete tarsometatarsi (~46.8 mm), phalanx II-1 (6.6 mm), phalanx II-2 (12.3 mm), partial pedal ungual II (11.7 mm), phalanx III-1 (10.7 mm), phalanx III-2
References- Chiappe and Calvo, 1989. El primer Enantiornithes (Aves) del Cretacico de Patagonia. Resumes VI Jornadas Argentinas de Paleontologia de Vertebrados. San Juan. pp. 19-21.
Chiappe, 1991. Cretaceous birds of Latin America. Cretaceous Research. 12(1), 55-63.
Chiappe, 1992. Enantiornithine (Aves) tarsometatarsi and the avian affinites of the Cretaceous Avisauridae. Journal of Vertebrate Paleontology. 12(3), 344-350.
Chiappe and Calvo, 1994. Neuquenornis volans, a new Late Cretaceous bird (Enantiornithes: Avisauridae) from Patagonia, Argentina. Journal of Vertebrate Paleontology. 14(2), 230-246.

Otogornis Hou, 1994
O. genghisi Hou, 1994
Early Cretaceous
Jingchuan (not Yijinholuo) Formation, Inner Mongolia, China
Holotype- (IVPP V9607) (~150 mm) scapulae (24 mm), coracoids (22 mm), humeri (31 mm), radii (40, 42 mm), ulnae (43, 50.1 mm), partial carpometacarpus, phalanx I-1(?), manual ungual I(?), feather impressions
Comments- Originally identified as an enantiornithine by Dong (1993), Hou (1994) later named the specimen and placed it as a basal enantiornithine. Kurochkin (1999) believed the taxon to be a palaeognath related to Ambiortus instead, assigning both to the Ambiortiformes.
References- Dong, 1993. A Lower Cretaceous enantiornithine bird from the Ordos Basin of Inner Mongolia, People's Republic of China. Canadian Journal of Earth Sciences. 30, 2177-2179.
Hou, 1994. A Late Mesozoic bird from Inner Mongolia. Vertebrata PalAsiatica. 32(4), 258-266 + 1 plate [in Chinese with English summary].
Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Kurochkin, 1999. The relationships of the Early Cretaceous Ambiortus and Otogornis (Aves: Ambiortiformes). Smithsonian Contributions to Paleobiology. 89: 275-284.

Paraprotopteryx Zheng, Zhang and Hou, 2007
P. gracilis Zheng, Zhang and Hou, 2007
Early Aptian, Early Cretaceous
Qiaotou Member of the Huajiying Formation, Hebei, China
Holotype- (STM V001) (subadult) several dorsal vertebrae, partial dorsal ribs, gastralia, pygostyle (12.9 mm), scapula (17.9 mm), coracoids (12.8 mm), partial sternum, sternal rib, incomplete humeri (22.6 mm), radii, ulnae (23.5 mm), radiales, ulnares, carpometacarpi (11.5 mm), manual phalanx I-1 (2.9 mm), manual ungual I, phalanx II-1 (5.5 mm), phalanx II-2 (3.5 mm), manual ungual II, phalanges III-1 (2.9 mm), phalanx III-2, manual claw sheath, incomplete femur (22.2 mm), tibiae (one partial; 26.3 mm), astragalocalcanea, metatarsals I, phalanges I-1, pedal unguals I, tarsometatarsi (15.7 mm), phalanges II-1, phalanges II-2, pedal unguals II, phalanx III-1, phalanx III-2, phalanx III-3, pedal ungual III, phalanges IV-1, phalanges IV-2, phalanges IV-3, phalanges IV-4, pedal unguals IV, remiges, retrices, body feathers
Other diagnoses- Zheng et al. (2007) list numerous additional characters in their diagnosis. The scapula is no longer (79%) than several other enantiornithines including the contemporaneous Jibeinia (86%). The elongation of the coracoid (length 2.37 times distal width, not 2.5 times as listed in the diagnosis) is very similar to Eoenantiornis (2.34) and in any case is intermediate between ratios in other enantiornithines. The authors state the furcula has two distinguishing features- an interclavicular angle of less than 40 degrees and a highly elongate hypocleideum (three-fourths of clavicular branch length). However, plate II shows that the supposed clavicular branches of the furcula are dorsal ribs while the illustrated hypocleidium is nowhere to be found in the photograph. This would explain the unusually slender clavicular branches in the illustration. The posteromedial sternal process is said to be longer and more robust than the posterolateral process, but the photograph indicates the supposed posterolateral process is probably a sternal rib instead. This leaves the supposed posteromedial process as the posterolateral process while the real posteromedial process is unpreserved with most of the posterior sternum. Manual ungual I is said to be larger than ungual II, but this seems to be merely due to the preserved keratinous sheath on ungual I, though larger manual ungual I's are known in some enantiornithines (e.g. Jibeinia). The length of manual digit I (76%- as measured from the base of the carpometacarpus to the tip of phalanx I-1 compared to the length of the semilunate carpal plus metacarpal II) is very similar to Jibeinia (71%) and especially Eoenantiornis (76%). Metacarpal III being more slender than metacarpal II is found in most theropods. Manual phalanx II-2 being shorter than II-1 is present in many derived enantiornithines. The carpometacarpus being only fused proximally is true in most enantiornithines. The unfused tibiotarsus is probably ontogenetic and is known in the young holotypes of other enantiornithines (Protopteryx, Rapaxavis, Dalingheornis, Jibeinia). Strong, curved pedal unguals and a long pygostyle are present in most enantiornithines. Finally, two pairs of elongate retrices are known in Shanweiniao.
Comments- While Zheng et al. (2007) refer Paraprotopteryx to the Liaoning Formation of Fengning, they also state Protopteryx, Jibeinia and Vescornis (= Hebeiornis) are from this locality. Jin et al. (2008) reassigned it to the Qiaotou Member of the Huajiying Formation. Zheng et al. state the skull "seems not to be the same individual as the postcranial bones after careful examination", and the portion of the slab containing the skull and cervical vertebrae does seem to contain an additional left coracoid.
Zheng et al. stated Paraprotopteryx was most similar to Protopteryx due to several characters. Of these, the unfused tibiotarsus is probably ontogenetic while the carpometacarpus is not unfused in Paraprotopteryx. Elongate paired retrices are also known in Jibeinia, Longirostravis, Shanweiniao and Dapingfangornis and seem standard for enantiornithines. The shared character of "complete manual claws" probably refers to the presence of two phalanges on digit III, which is seen in all basal enantiornithines including Pengornis, Jibeinia, Longipteryx, Longirostravis, Rapaxavis and Eocathayornis.
References- Zheng, Zhang and Hou, 2007. A new enantiornithine bird with four long retrices from the Early Cretaceous of Northern Hebei, China. Acta Geologica Sinica. 81(5), 703-708.
Jin, Zhang, Li, Zhang, Li and Zhou, 2008. On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota. Chinese Science Bulletin. 53(18), 2820-2827.

Euenantiornithes Chiappe, 2002
Definition- (Sinornis santensis <- Iberomesornis romerali) (modified from Chiappe, 2002)
Cathayornithiformes Zhou, Jin and Zhang, 1992
= Sinornithiformes Hou, 1997
Cathayornithidae Zhou, Jin and Zhang, 1992
= Sinornithidae Hou, 1997
References- Zhou, Jin and Zhang, 1992. Preliminary report on a Mesozoic bird from Liaoning, China. Chinese Science Bulletin. 37 1365-1368.
Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Sinornis Sereno and Rao, 1992
= Cathayornis Zhou, Jin and Zhang, 1992
S. santensis Sereno and Rao, 1992
= Cathayornis yandica Zhou, Jin and Zhang, 1992
?= Cathayornis "shanwangensis" Xu, Yang and Deng, 1999
Early Albian, Early Cretaceous
Jiufotang Formation, Liaoning, China
Holotype- (BPV 538) incomplete skull (~26.5 mm), partial mandibles, eleven dorsal vertebrae (2.4, 2.3 mm; dorsal column ~30.5 mm), dorsal ribs, sacrum (12.9 mm; first sacral 2.5 mm, eighth sacral 1.5 mm), first caudal vertebra (1.6 mm), second caudal vertebra (1.5 mm), third caudal vertebra (1.5 mm), fourth caudal vertebra (1.3 mm), fifth caudal vertebra (1 mm), sixth caudal vertebra (.6 mm), five chevrons, pygostyle (11.5 mm), scapula (~18 mm), partial coracoid, furcula, partial sternum, incomplete humerus (24 mm), partial radii (~22.2 mm), partial ulnae (~19.2 mm), radiale, ulnare, carpometacarpus (10.3 mm; metacarpal I ~1.9 mm, metacarpal III ~10.8 mm), phalanx I-1 (4 mm), manual ungual I (1.6 mm), phalanx II-1 (5.4 mm), phalanx II-2 (3.8 mm), manual ungual II (2.1 mm), phalanx III-1 (3.9 mm), incomplete ilium (~13 mm), pubes, ischia, femora (~21 mm), tibiotarsi (25.7, 26.4 mm), fibulae, metatarsal I (3.2 mm), phalanx I-1 (3.7 mm), pedal ungual I (5.6 mm), tarsometatarsi (metatarsal II 14.1 mm, metatarsal III 14.6 mm, metatarsal IV 14.1 mm), phalanx II-1 (3.2 mm), phalanx II-2 (4.1 mm), pedal ungual II (5.8 mm), phalanx III-1 (4.3 mm), phalanx III-2 (3.6 mm), phalanx III-3 (3.9 mm), pedal ungual III (6.7 mm), phalanx IV-1 (2.1 mm), phalanx IV-2 (2.1 mm), phalanx IV-3 (2.1 mm), phalanx IV-4 (3 mm), pedal ungual IV (5.3 mm)
Referred- (IVPP V 9769; holotype of Cathayornis yandica) incomplete skull (28.2 mm), mandibles, five cervical vertebrae (2.7, 2.5 mm), fourth(?) dorsal vertebra (2.5 mm), dorsal ribs, sacrum (13.1 mm), first caudal vertebra (2 mm), second caudal vertebra, third caudal vertebra, fourth caudal vertebra, fifth caudal vertebra (1.6 mm), sixth caudal vertebra, pygostyle (14.4 mm), scapulae (19.6 mm), coracoid, furcula, partial sternum, humeri (27 mm), radii (25.3 mm), ulnae (26.4 mm), radiale, ulnare, carpometacarpi (11.5 mm; metacarpal I 2.2 mm, metacarpal III 13 mm), phalanx I-1 (4.7 mm), manual ungual I (1.8 mm), phalanx II-1 (6.9 mm), phalanx II-2 (4.2 mm), manual ungual II (1.8 mm), phalanx III-1 (3.3 mm), ilia (13.9 mm), pubes, ischium, femora (23.1 mm), tibiotarsi (29 mm), fibulae, metatarsal I (3 mm), tarsometatarsus (metatarsal II 14.8 mm), several pedal phalanges, three pedal unguals (Zhou, Jin and Zhang, 1992)
?(IVPP V9936) tarsometatarsus, seven pedal phalanges, two pedal unguals (Zhou and Hou, 2002)
?(IVPP V10896) specimen including cranial elements (Martin and Zhou, 1997)
References- Sereno and Rao, 1992. Early Evolution of Avian Flight and Perching: New Evidence from the Lower Cretaceous of China. Science. 255, 845-848.
Zhou, Jin and Zhang, 1992. Preliminary report on a Mesozoic bird from Liaoning, China. Chinese Science Bulletin. 37 1365-1368.
Zhou, 1995. Discovery of Early Cretaceous birds in China. Courier Forschungsinstitut Senckenberg. 181, 9–23.
Zhou, 1995. New understanding of the evolution of the limb and girdle elements in early birds - evidences from Chinese fossils. In Sun and Wang (eds.). Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota. Short papers, 209-214.
Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Martin and Zhou, 1997. Archaeopteryx-like skull in Enantiornithine bird. Nature. 389, 556.
Xu, Yang and Deng, 1999. First discovery of Mesozoic bird fossils in Hebei Province and its significance. Regional Geology of China. 18(4), 444-448.
Sereno, Rao and Li, 2002.Sinornis santensis (Aves: Enantiornithes) from the Early Cretaceous of Northeastern China. pp 184-208. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Zhou and Hou, 2002. The Discovery and Study of Mesozoic Birds in China. pp 160-183. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

Soroavisaurus Chiappe, 1993
S. australis Chiappe, 1993
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Holotype- (PVL-4690) (~345 mm) tarsometatarsus (46.9 mm; metatarsal II 44.2, metatarsal IV 43.3 mm)
Paratype- (PVL-4048) metatarsal I (12.2 mm), phalanx I-1 (16.2 mm), ungual I (17.3 mm), tarsometatarsus (51.5 mm; metatarsal II 48.9, metatarsal IV 48.4 mm), four pedal phalanges
Reffered- ?(PVL-4030) distal tibiotarsus (Chiappe and Walker, 2002)
?(PVL-4033) tibiotarsus (Walker, 1981)
Comments- PVL-4048 was originally illustrated by Walker (1981). Brett-Surman and Paul (1985) made it and PVL-4690 paratypes of Avisaurus archibaldi, though they referred to PVL-4060 as Avisaurus sp. and 4048 as Avisauridae in an illustration. They were also referred to Avisaurus sp. by Chiappe (1992) and Chiappe and Calvo (1994). Chiappe (1993) named them both Soroavisaurus australis. PVL-4033 was also originally illustrated by Walker, but not referred to Soroavisaurus until Chiappe and Walker (2002). The latter authors also referred PVL-4030 to Soroavisaurus and illustrated both tibiotarsi. The rationale for this referral is unknown, though it is possible the articular surface and/or size matched Soroavisaurus better than Yungavolucris (the tibiotarsus of Lectavis is known). Still, there are at least five enantiornithines from that assemblage (as shown by humeri), and Soroavisaurus has a more standard metatarsal morphology than Yungavolucris or Lectavis, so I'm not certain about the referral at this time. Walker et al. (2007) noted PVL-4033 is consistant in size with both Enantiornis and Martinavis.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Brett-Surman and Paul, 1985. A new family of bird-like dinosaurs linking Laurasia and Gondwanaland. Journal of Vertebrate Paleontology. 5(2), 133-138.
Chiappe, 1992. Enantiornithine (Aves) tarsometatarsi and the avian affinites of the Cretaceous Avisauridae. Journal of Vertebrate Paleontology. 12(3), 344-350.
Chiappe, 1993. Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates. 3083, 39 pp.
Chiappe and Calvo, 1994. Neuquenornis volans, a new Enantiornithes (Aves) from the Upper Cretaceous of Patagonia (Argentina). Journal of Vertebrate Paleontology. 14, 230–246.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

Yungavolucris Chiappe, 1993
Y. brevipedalis Chiappe, 1993
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Holotype- (PVL-4053) (~340 mm) tarsometatarsus (41.9 mm)
Paratypes- (PVL-4040) incomplete tarsometatarsus (41.6 mm)
(PVL-4052) incomplete tarsometatarsus (51.9 mm) (Chiappe, 1991)
(PVL-4268) distal metatarsal II, distal metatarsal III
(PVL-4692) distal tarsometatarsus (42.8 mm)
Comments- Walker et al. (2007) mistakenly assigned the holotype to Avisaurus.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Chiappe, 1991. Cretaceous birds of Latin America. Cretaceous Research. 12(1), 55-63.
Chiappe, 1993. Enantiornithine (Aves) tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates. 3083, 39 pp.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

unnamed enantiornithine (Gilmore, 1920)
Late Cretaceous
Lance Formation, Wyoming, US
Material- (USNM 2909) distal metatarsal II, two distal pedal phalanges
Comments- Originally referred to Ornithomimus minutus by Gilmore (1920), but later to Euenantiornithes by Chiappe and Walker (2002).
References- Gilmore, 1920. Osteology of the Carnivorous dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus. United States National Museum, Bulletin No. 110, pp. 1-154.
Chiappe, L. M., and Walker, C. A. (2002) Skeletal morphology and systematics of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes): In: Mesozoic Birds, above the heads of Dinosaurs, University of California Press, 240-267.

unnamed Enantiornithes (Walker, 1981)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (MACN-S-01) femur (93.5 mm) (Chiappe and Calvo, 1994)
(PVL-4037) femur (Walker, 1981)
(PVL-4038) femur (Chiappe and Calvo, 1994)
Comments- PVL-4037 was illustrated by Walker (1981) and Chiappe and Walker (2002), while the other two specimens were first noted by Chiappe and Calvo (1994). Chinsamy et al. (1995) examined the histology of MACN-S-01. Walker et al. (2007) stated PVL-4037 is consistant in size with both Enantiornis and Martinavis? vincei from the same locality. These three femora are all from enantiornithines based on their hypertrophied posterior trochanters. In addition, they resemble Vorona, Neuquenornis and Concornis in having a posteriorly projected lateral border on the distal femur.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Chiappe and Calvo, 1994. Neuquenornis volans, a new Enantiornithes (Aves) from the Upper Cretaceous of Patagonia (Argentina). Journal of Vertebrate Paleontology. 14, 230-246.
Chinsamy, Chiappe and Dodson, 1995. Mesozoic avian bone microstructure: Physiological implications. Paleobiology. 21(4), 561-574.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

unnamed enantiornithine (Walker, 1981)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (PVL-4022) humerus (Chiappe and Walker, 2002)
Comments- PVL-4022 is a humerus illustrated by Chiappe and Walker (2002), though noted (without reference to a specimen number) as early as Walker (1981) for being unique among Lecho enantiornithines in having a pneumotricipital foramen. It's an enantiornithine based on- well-developed fossa on the midline of the proximal humerus making the articular surface appear V-shaped in proximal view; ventrodistal margin of humerus projected significantly distal to dorsodistal margin, distal margin angling strongly ventrally (also in Piksi and Apsaravis); proximoposterior surface of deltopectoral crest concave (also in Confuciusornis, Apsaravis and Ichthyornis); long axis of dorsal condyle of humerus almost transversely oriented (also in Yanornis and Apsaravis). Within Enantiornithes, it is derived based on the proximal edge of humeral head which is centrally concave and the hypertrophied bicipital crest. It appears to be a different taxon than Enantiornis, Martinavis? vincei, PVL-4025 and PVL-4035.
References- Walker, 1981. New subclass of birds from the Cretaceous of South America. Nature. 292, 51-53.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

undescribed enantiornithine (Martin and Stewart, 1982)
Campanian, Late Cretaceous
Pembina Member of the Vermillion River Formation, Manitoba, Canada
Material- (CFDC B.77.03.07) dorsal vertebra (6 mm)
Comments- Referred to Ichthyornis sp. by Martin and Stewart (1982), and later to Enantiornithes by Clarke (2004) because of its centrally placed parapophyses.
References- Martin and Stewart, 1982. An ichthyornithiform bird from the Campanian of Canada. Canadian Journal of Earth Sciences. 19, 324-327.
Nicholls, 1989. Marine vertebrates of the Pembina Member of the Pierre Shale (Campanian, Upper Cretaceous) of Manitoba and their significance to the biogeography of the Western Interior Seaway. University of Calgary.
Clarke, 2004. Morphology, phylogenetic taxonomy, and systematics of Ichthyornis and Apatornis (Avialae: Ornithurae). Bulletin of the American Museum of Natural History. 286: 1-179.

unnamed enantiornithine (Nessov and Borkin, 1983)
Mid-Late Turonian, Late Cretaceous
Bissekty Formation, Uzbekistan
Material- (PO 3494) proximal tarsometatarsus
Comments- Discovered in 1979, this was identified as an enantiornithid by Nessov and Borkin (1983), then as an enantiornithiform by Nessov (1984, 1992). Kurochkin (1996) referred it to Alexornithidae within Enantiornithes. This was based on the strongly reduced metatarsal IV, which however seems to characterize most enantiornithines except for Aberratiodontus, Iberomesornis, Liaoningornis and Vorona. The extremely enlarged medial tibiotarsal condyle (based on the tarsometatarsal cotyla it was ~225% the width of the lateral condyle) is characteristic of a derived set of enantiornithines including Gobipteryx, Nanantius and Soroavisaurus though.
References- Nessov and Borkin, 1983. New records of bird bones from the Cretaceous of Mongolia and Soviet Middle Asia. USSR Academy of Sciences, Proceedings of the Zoological Institute. 116, 108-110 (in Russian).
Nessov, 1984. [Upper Cretaceous pterosaurs and birds from Central Asia] Paleontologicheskii Zhurnal. 1, 47-57.
Nessov, 1992. Mesozoic and Paleogene birds of the USSR and their paleoenvironments. in Campbell (ed). Papers in Avian Paleontology Honoring Pierce Brodkorb. Natural History Museum of Los Angeles County Science Series. 36, 465-478.
Kurochkin, 1996. A new enantiornithid of the Mongolian Late Cretaceous, and a general appraisal of the Infraclass Enantiornithes (Aves). Russian Academy of Sciences, special issue. 50 pp.

unnamed enantiornithine (Chiappe, 1991)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (PVL-4043) proximal humerus (Chiappe, 1991)
Comments- This proximal humerus was photographed by Chiappe (1991) and is an enantiornithine based on the well-developed fossa on the midline of the proximal humerus, making the articular surface appear V-shaped in proximal view. Additional characters shared with derived enantiornithines include the proximally concave humeral head and hypertrophied bicipital crest. It appears to be a different taxon than Enantiornis, Martinavis? vincei, PVL-4022, PVL-4025. It may belong to Lectavis, Soroavisaurus or Yungavolucris.
Reference- Chiappe, 1991. Cretaceous birds of Latin America. Cretaceous Research. 12(1), 55-63.

unnamed Enantiornithes (Chiappe and Calvo, 1994)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (PVL-4041-2) two dorsal vertebrae
(PVL-4051) six dorsal vertebrae
Comments- These vertebrae were first reported and commented on by Chiappe and Calvo (1994), and later illustrated by Chiappe and Walker (2002). Both of these specimens are Enantiornithes at least as derived as Iberomesornis due to the centrally located posterior dorsal parapophyses. They may belong to Yungavolucris, Enantiornis and/or Soroavisaurus.
References- Chiappe and Calvo, 1994. Neuquenornis volans, a new Enantiornithes (Aves) from the Upper Cretaceous of Patagonia (Argentina). Journal of Vertebrate Paleontology. 14, 230–246.
Chiappe, 1996. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. Munchner Geowissenschaftliche Abhandlungen (A). 30, 203–244.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

unnamed enantiornithine (Chiappe and Calvo, 1994)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (PVL-4029) incomplete coracoid (Chiappe and Calvo, 1994)
Comments- PVL-4029 is a coracoid illustrated by Chiappe and Calvo (1994).
Reference- Chiappe and Calvo, 1994. Neuquenornis volans, a new Enantiornithes (Aves) from the Upper Cretaceous of Patagonia (Argentina). Journal of Vertebrate Paleontology. 14, 230–246.

unnamed enantiornithine (Chiappe, 1996)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (PVL-4025) humerus (95.2 mm) (Chiappe, 1996)
Comments- PVL-4025 is a humerus first photographed as Enantiornithes by Chiappe (1996), and later illustrated by Chiappe and Walker (2002). Walker et al. (2007) assigned it to Martinavis sp.. However, PVL-4025 does not have some supposed Martinavis characters listed by Walker et al. (deltopectoral crest merges smoothly into shaft; bicipital crest small and anteriorly angled; large ventral epicondyle), and there are no characters which it uniquely shares with M. cruzyensis and/or vincei. In addition, the authors mention it differs from Martinavis in several characters- low deltopectoral crest; deltopectoral crest does not merge smoothly into shaft (shared with Enantiornis); capital groove closed proximally (perhaps unique among enantiornithines); pneumotricipital fossa extends onto base of ventral tubercle. It seems best to keep this specimen out of Martinavis, and it could be named as a new taxon.
References- Chiappe, 1996. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. Munchner Geowissenschaftliche Abhandlungen (A). 30, 203–244.
Chiappe and Walker, 2002. Skeletal morphology and systematic of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). pp 240-267. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

unnamed Enantiornithes (Chiappe, 1996)
Maastrichtian, Late Cretaceous
Lecho Formation, Argentina
Material- (PVL-4028) incomplete humerus (Chiappe, 1996)
(PVL-4046) incomplete humerus (Chiappe, 1996)
Comments- PVL-4046 and 4028 were first listed as Enantiornithes by Chiappe (1996), and later assigned by Walker et al. (2007) to Martinavis sp.. Neither specimen has been illustrated however, the supposed apomorphies of Martinavis are not valid (see Martinavis Other diagnoses), and there are no characters which it uniquely shares with M. cruzyensis and/or vincei.. Walker et al. did state PVL-4025 differs from 4046 in having a shorter deltopectoral crest, deeper pneumotricipital fossa, more enlarged and bulbous dorsal tubercle and more anteriorly projected bicipital crest. Thus, they may not even be congeneric and are best kept out of Martinavis.
References- Chiappe, 1996. Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi. Munchner Geowissenschaftliche Abhandlungen (A). 30, 203–244.
Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

unnamed enantiornithine (Sanz, Chiappe, Perez-Moreno, Moratalla, Hernandez-Carrasquilla, Buscalioni, Ortega, Poyato-Ariza, Rasskin-Gutman and Martinez-Delclos, 1997)
Late Berriasian-Early Barremian, Early Cretaceous
La Pedrera de Rubies Lithographic Limestones, Spain
Material- (LP-4450-IEI) (juvenile) skull, mandible, hyoids, nine cervical vertebrae, partial dorsal ribs, scapula, coracoid, furcula, humerus, radius, ulna, carpometacarpus, phalanx I-1, manual ungual I, phalanx II-1, phalanx II-2, manual ungual II, feather impressions
References- Sanz, Chiappe, Perez-Moreno, Moratalla, Hernandez-Carrasquilla, Buscalioni, Ortega, Poyato-Ariza, Rasskin-Gutman and Martinez-Delclos, 1997. A nestling bird from the Lower Cretaceous of Spain: Implications for avian skull and neck evolution. Science. 276, 1543-1546.
Marugan-Lobon, Cambra-Moo, Martinez-Delclos, Sanz and Buscalioni, 2002. Juvenile enantiornithine skeleton from Montsec (Catalonia, Spain) Lower Cretaceous revisited: Taphonomy and morphometrics to access ontogenetic stage. Journal of Vertebrate Paleontology. 22(3), 84A.

unnamed enantiornithine (Buffetaut, Mechin and Mechin-Salessy, 2000)
Early Maastrichtian, Late Cretaceous
Bastide-Neuve, Provence, France
Material- (Mechin coll. no. 606) tibiotarsus (132 mm)
Comments- Buffetaut et al. (2000) referred this specimen to Enantiornithes incertae sedis. The reduced fibula indicates this is an ornithurine (sensu Gauthier), while the tubercle on the ascending process is a pygostylian character. Although uncommon, lack of fusion between the astragalocalcaneum and tibia is known in some pygostylians (e.g. Longipteryx, Hebeiornis, Gobipteryx, Vorona) and may be ontogenetic. The lack of medially tapering distal condyles and narrow intercondylar groove are seen in most enantiornithines, but also the basal ornithuromorphs Apsaravis and PKUP 1069. The large medial condyle (~200% the width of the lateral one) is characteristic of a subset of enantiornithines, including Nanantius, Gobipteryx and Soroavisaurus.
Reference- Buffetaut, Mechin and Mechin-Salessy, 2000. An archaic bird (Enantiornithes) from the Upper Cretaceous of Provence (Southern France). Comptes Rendus de l'Academie des Sciences. 331, 557-561.

undescribed enantiornithine (Sanz, Chiappe, Fernadez-Jalvo, Ortega, Sanchez-Chillon, Poyato-Ariza and Perez-Moreno, 2001)
Late Barremian, Early Cretaceous
Calizas de La Huerguina Formation, Spain
Material- (LH 11386 bird 1) (juvenile) four posterior cervical vertebrae, eleven dorsal vertebrae, dorsal neural spine, six dorsal ribs, sacrum, twelve caudal vertebrae(?), scapulae, coracoids, sternum, sternal ribs, humerus, radius, ulna, ulnare, phalanx I-1, manual ungual I, distal metacarpal II, proximal phalanx II-1, partial ilium, proximal pubis, ischium, partial femur, astragalus, metatarsal I, phalanx I-1, pedal ungual I, metatarsal II, phalanx II-1, phalanges II-2, pedal unguals II, metatarsal III, phalanx III-1, phalanges III-2, phalanges III-3, pedal ungual III, metatarsal IV, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV, fragments, remiges
Comments- This specimen is the most complete of four juvenile birds found associated in a theropod or pterosaur pellet. It was only identified as a bird by Sanz et al. (2001), and colored dark gray in their illustration. The strut-like coracoid and tapered distal scapula are like ornithurines sensu Gauthier (though confuciusornithids reverse the latter). The fused sterna are similar to euavialans, though its small size and lack of lateral processes are no doubt due to its young age, as seen in juvenile enantiornithines and confuciusornithids. Several characters are unlike most ornithuromorphs, but similar to enantiornithines and more basal birds. The absent procoracoid process is only found in Patagopteryx and Apsaravis. The scapula being shorter than the humerus is only found in Archaeorhynchus, Yanornis and Gansus. The medial tibiotarsal condyle being wider than the lateral one is only seen in Patagopteryx. Finally, the proximal end of metatarsal III is in the same plane as metatarsals II and IV, which is only seen in Patagopteryx, Archaeorhynchus and Hongshanornis among ornithuromorphs. Other characters are shared only with enantiornithines with a few exceptions. The deep dorsal coracoid fossa and narrow tibiotarsal intercondylar groove (~25% of tibiotarsal width) are only present in enantiornithines and Apsaravis. The narrow sternal xiphoid process is only present in enantiornithines and Hongshanornis. Metatarsal IV being so narrow compared to II and III is uniquely enantionithine. Within Enantiornithes, the specimen may be more derived than Protopteryx, Longipteryx and Eoenantiornis based on its short manual digit I. The sternal xiphoid process is distally expanded as in Longirostravis, Shanweiniao, Eocathayornis, Eoalulavis and Liaoningornis. Yet metatarsal II has a trochlea smaller than III, which among enantiornithines is only known in longipterygids, Vorona and Liaoningornis. It may be most closely related to Vorona, Liaoningornis, or Shanweiniao and Longirostravis.
Reference- Sanz, Chiappe, Fernadez-Jalvo, Ortega, Sanchez-Chillon, Poyato-Ariza and Perez-Moreno, 2001. An Early Cretaceous pellet. Nature. 409, 998-999.

unnamed enantiornithine (Walker, Buffetaut and Dyke, 2007)
Campanian, Late Cretaceous
Lance's Quarry, New Mexico, US
Material- (KU-NM-37) proximal humerus
Comments- Walker et al. (2007) refer this to Martinavis sp., but the supposed apomorphies of that genus are not valid (see Martinavis Other diagnoses) and there are no characters which it uniquely shares with M. cruzyensis and/or vincei. The authors confusingly stated it is "the most distinctive of [the] referred specimens" and that it "is indistinguishable from other bones referred here to Martinavis." The broad capital groove is more similar to M. cruzyensis, while the broad pneumotricipital groove is more similar to M? vincei. It seems best to keep this specimen out of Martinavis.
Reference- Walker, Buffetaut and Dyke, 2007. Large euenantiornithine birds from the Cretaceous of southern France, North America and Argentina. Geological Magazine. 144(6), 977-986.

Liaoningornithiformes Hou, 1996
Liaoningornithidae Hou, 1996
Diagnosis- (proposed) sternum elongate (unknown in Vorona); posteromedial sternal processes absent (also in taxa less derived than Longipteryx; unknown in Vorona); posterolateral sternal processes absent (unknown in Vorona); posteromedian process of sternum extremely expanded (unknown in Vorona); metatarsals at least partially fused distally (also in Changchengornis, Avisaurus gloriae and Euornithes; unknown in Eoalulavis); trochlea of metatarsal II subequal in width to III (also in non-enantiornithines and Longipterygidae; unknown in Eoalulavis); metatarsal IV not reduced in width compared to II and III (also in non-enantiornithines and those more basal than Longipteryx; unknown in Eoalulavis).
Reference- Hou, 1996. The discovery of a Jurassic carinate bird in China. Chinese Science Bulletin. 41(2). 1861-1864 (in Chinese).

Eoalulavis Sanz, Chiappe, Perez-Moreno, Buscalioni, Moratalla, Ortega and Poyato-Ariza, 1996
E. hoyasi Sanz, Chiappe, Perez-Moreno, Buscalioni, Moratalla, Ortega and Poyato-Ariza, 1996
Late Barremian, Early Cretaceous
Calizas de La Huerguina Formation, Spain
Holotype- (LH-13500) (~150 mm; adult) five posterior cervical vertebrae, ten dorsal vertebrae, several dorsal ribs, scapulae, coracoids (17 mm), furcula, sternum, humeri (27 mm), radii, ulnae (31 mm), ulnare, metacarpal I, phalanx I-1, manual ungual I, metacarpal II, phalanx II-1, phalanx II-2, manual ungual II, metacarpal III, phalanx III-1, ilium, proximal femur, feather impressions
References- Sanz, Chiappe, Perez-Moreno, Buscalioni, Moratalla, Ortega and Poyato-Ariza, 1996. An Early Cretaceous bird from Spain and its implications for the evolution of avian flight. Nature. 382, 442-445.
Sanz, Pérez-Moreno, Chiappe and Buscalioni, 2002. The Birds from the Lower Cretaceous of Las Hoyas (Privince of Cuenca, Spain). pp 209-229. in Chiappe and Witmer (eds.). Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

Liaoningornis Hou, 1996
L. longidigitus Hou, 1996
Late Barremian-Early Aptian, Early Cretaceous
Jianshangou Beds of Yixian Formation, Liaoning, China
Holotype- (IVPP V11303) (~150 mm) partial dorsal ribs, gastralia, partial scapula or pubis, partial coracoid, sternum, partial furcula(?), distal humerus, proximal radius, proximal ulna, distal pubis, femur, tibiotarsus, fibula, metatarsal I, phalanx I-1, pedal ungual I, tarsometatarsi, phalanx II-1, phalanx II-2, pedal ungual II, phalanx III-1, phalanx III-2, phalanx III-3, phalanx IV-1, phalanx IV-2, phalanx IV-3, phalanx IV-4, pedal ungual IV
Comments- This specimen has a number of controversial element identifications. An element identified as a scapula by Hou (1997) was identified as a pubis by Zhou and Hou (2002). Another pubis identified by the latter authors was unlabeled in Hou (1997). The coracoid is interpreted as laying with its lateral edge against the sternum by Hou, but with its distal edge against the sternum (in articulation?) by Zhou and Hou. Finally, an elongate bone was identified as a hypocleidium by Hou, but as part of the sternal keel by Zhou and Hou. Clarke (2002) agrees with the former identification.
References- Hou, 1996. The discovery of a Jurassic carinate bird in China. Chinese Science Bulletin. 41(2). 1861-1864 (in Chinese).
Hou, Martin, Zhou and Feduccia, 1996. Early adaptive radiation of birds: Evidence from fossils from Northeastern China. Science. 274, 1164-1167.
Hou, 1997. A carinate bird from the Upper Jurassic of Western Liaoning, China. Chinese Science Bulletin. 42(5), 413-417.
Hou, 1997. Mesozoic Birds of China. Phoenix Valley Bird Park, Lugu Hsiang, Taiwan. 221 pp.
Clarke, 2002. The morphology and systematic position of Ichthyornis Marsh and the phylogenetic relationships of basal Ornithurae. Ph.D. dissertation, Yale University, New Haven, CT, 532 pp.
Zhou and Hou, 2002. The Discovery and Study of Mesozoic Birds in China. pp 160-183. in Chiappe and Witmer, (eds.). Mesozoic Birds – Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.

Vorona Forster, Chiappe, Krause and Sampson, 1996
V. berivotrensis Forster, Chiappe, Krause and Sampson, 1996
Maastrichtian, Late Cretaceous
Maevarano Formation, Madagascar
Holotype- (UA 8651) (~510 mm) distal tibiotarsus, tarsometatarsus (60.9 mm; metatarsal II 53.8 mm, metatarsal III 61 mm, metatarsal IV 58.4 mm, metatarsal V 16.4 mm)
Paratype- (FMNH PA 715) (~540 mm) incomplete femur (93.7 mm), tibiotarsus (165.8 mm), incomplete fibula
Referred- (FMNH PA 717) incomplete femur (94.1 mm) (Forster et al., 2002)
? two partial humeri, ulna (Forster and O'Connor, 2000)
Comments- Using the tibiotarsus to estimate gives a length of 690 mm, while using the metatarsus gives a length of 460 mm. I decided to use tibial diameter, figuring this would remain more constant in different taxa. This gives the 540 mm estimate above, which seems appropriate. This is based off the referred specimen, the holotype was about 6% smaller, or about 510 mm long.
The forelimb elements were assigned based on morphological and morphometric evidence.
References- Forster, Chiappe, Sampson, Krause, 1996. The first Cretaceous bird from Madagascar. Nature. 382, 532-534.
Forster and O'Connor, 2000. The avifauna of the Upper Cretaceous Maevarano Formation, Madagascar. Journal of Vertebrate Paleontology. 20(3), 41A-42A.
Forster, Chiappe, Krause and Sampson, 2002. Vorona berivotrensis, a primitive bird from the Late Cretaceous of Madagascar. 268-280. in Chiappe and Witmer (eds.). Mesozoic Birds: Above the Heads of Dinosaurs. University of California Press, Berkeley, Los Angeles, London.