Belongs within: Avialae.
Contains: Ornithurae, Euenantiornithes.
The Ornithothoraces is the clade uniting the modern birds with the Enantiornithes, a clade of stem birds that was significant in the Cretaceous but did not survive the end of the Mesozoic. The name ‘Ornithothoraces’ refers to the develop of an enlarged, keeled sternum allowing a greater surface for the attachment of the flight muscles. The Enantiornithes were morphologically and ecologically diverse, including both toothed and toothless forms. They exhibited a distinct mode of fusion of the foot bones from the lineage leading to modern birds, with the metatarsals fusing from the ankle towards the toes instead of from the midpoint towards both ends as in the latter lineage (Padian 2004). Other early Ornithothoraces include Vorona berivotrensis from the Late Cretaceous of Madagascar.
Synapomorphies (from Clarke 2004): Eight or nine ankylosed sacral vertebrae; ossified sternal plates fused with projected keel; scapula and coracoid unfused; angle between coracoid and scapula at glenoid 90° or less; scapula tapering distally; humerus with ventral tubercle and capital incisure present, transverse groove present (developed as discrete, depressed scar on proximal surface of bicipital crest or as slight transverse groove), bicipital crest developed as anterior projection relative to shaft surface in ventral view; distal end of dorsal condyle of ulna with dorsal trochlear surface developed as semilunate ridge; semilunate carpal and metacarpals completely fused proximally; pisiform process present; tibia/tarsal formed condyles equal in anterior projection.
<==OrnithothoracesC04 | i. s.: Kuszholia Nessov 1992P04 | `--K. mengi Nessov 1992P04 |--OrnithuromorphaP04 | |--ArchaeorhynchusWSZ18 | `--+--Jianchangornis microdontaWSZ18, MWL11 | `--+--OrnithuraeC04 | `--+--BellulornisWSZ18 | `--SchizoouraWSZ18 `--EnantiornithesC04 | i. s.: Aberratiodontus Gong, Hou & Wang 2004 [Aberratiodontuidae, Aberratiodontuiformes]GHW04 | `--*A. wui Gong, Hou & Wang 2004GHW04 | Zhyraornis Nessov 1984 [Zhyraornithidae]P04 | |--Z. kashkarovi Nessov 1984P04 | `--Z. logunovi Nessov 1992P04 | ‘Ichthyornis’ minusculus Nessov 1990 (n. d.)C04, P04 | Gurilynia Kurochkin 1999P04 | `--G. nessovi Kurochkin 1999P04 | Halimornis Chiappe, Lamb & Ericson 2002P04 | `--H. thompsoni Chiappe, Lamb & Ericson 2002P04 | Kizylkumavis Nesson 1984P04 | `--K. cretacea Nessov 1984P04 | Lectavis Chiappe 1993P04 | `--L. bretincola Chiappe 1993P04 | Lenesornis Kurochkin 1996P04 | `--L. maltshevskyi (Nessov 1986) [=Ichthyornis maltshevskyi]P04 | Otogornis Hou 1994P04 | `--O. genghisi Hou 1994P04 | Soroavisaurus Chiappe 1993P04 | `--S. australis Chiappe 1993P04 | Yungavolucris Chiappe 1993P04 | `--Y. brevipedalis Chiappe 1993P04 | EnantiornithiformesU93 | | i. s.: Nanantius Molnar 1986U93, P04 | | `--N. eos Molnar 1986P04 | |--Alexornis Brodkorb 1976P04 [AlexornithidaeU93] | | `--A. antecedens Brodkorb 1976P04 | |--Avisaurus Brett-Surman & Paul 1985P04 [AvisauridaeU93] | | |--A. archibaldi Brett-Surman & Paul 1985P04 | | `--A. gloriae Varricchio & Chiappe 1995P04 | `--EnantiornithidaeU93 | |--Sazavis Nessov & Yarkov 1989U93, P04 | | `--S. prisca Nessov & Yarkov 1989P04 | `--Enantiornis Walker 1981P04 | |--E. leali Walker 1981P04 | |--E. martini Nessov & Panteleyev 1993P04 | `--E. walkeri Nessov & Panteleyev 1993P04 | Liaoxiornis Hou & Chen 1999 [=Lingyuanornis]D07 | `--L. delicatusSD11 | Iberomesornis Sanz & Bonaparte 1992 [Iberomesornithidae, Iberomesornithiformes]P04 | `--I. romerali Sanz & Bonaparte 1992P04 | Noguerornis Lacasa-Ruiz 1989P04 | `--N. gonzalezi Lacasa-Ruiz 1989P04 |--PengornisWSZ18 |--EopengornisWSZ18 |--Protopteryx Zhang & Zhou 2000WSZ18, P04 | `--P. fengningensis Zhang & Zhou 2000P04 `--+--MonoenantiornisWSZ18 `--+--BohaiornithidaeWSZ18 | |--ShenqiornisWSZ18 | |--SulcavisWSZ18 | `--+--LongusunguisWSZ18 | `--+--ZhouornisWSZ18 | `--+--ParabohaiornisWSZ18 | `--BohaiornisWSZ18 `--+--FortunguavisWSZ18 `--+--LinyiornisWSZ18 `--+--Eoenantiornis Hou, Martin et al. 1999WSZ18, P04 | `--E. buhleri Hou, Martin et al. 1999P04 `--+--EuenantiornithesWSZ18 |--CruralispennisWSZ18 |--QilianiaWSZ18 |--PterygornisWSZ18 |--PiscivorenantiornisWSZ18 |--VescornisWSZ18 |--+--DunhuangiaWSZ18 | `--ElsornisWSZ18 `--+--Eocathayornis Zhou 2002WSZ18, P04 | `--E. walkeri Zhou 2002P04 `--Longipterygidae [Longipterygiformes]WSZ18 |--+--ShanweiniaoWSZ18 | `--+--RapaxavisWSZ18 | `--LongirostravisWSZ18 `--+--Longipteryx Zhang, Zhou et al. 2001WSZ18, ZZ01 | `--*L. chaoyangensis Zhang, Zhou et al. 2001ZZ01 `--Boluochia Zhou 1995WSZ18, P04 `--B. zhengi Zhou 1995P04
*Type species of generic name indicated
References
[C04] Clarke, J. A. 2004. Morphology, phylogenetic taxonomy, and systematics of Ichthyornis and Apatornis (Avialae: Ornithurae). Bulletin of the American Museum of Natural History 286: 1–179.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
[GHW04] Gong E., Hou L. & Wang L. 2004. Enantiornithine bird with diapsidian skull and its dental development in the Early Cretaceous in Liaoning, China. Acta Geologica Sinica (English Edition) 78 (1): 1–7.
[MWL11] Meng, J., Y. Wang & C. Li. 2011. Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont. Nature 472: 181–185.
[P04] Padian, K. 2004. Basal Avialae. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria 2nd ed. pp. 210–231. University of California Press: Berkeley.
[SD11] Sun, G., D. L. Dilcher, H. Wang & Z. Chen. 2011. A eudicot from the Early Cretaceous of China. Nature 471: 625–628.
[U93] Unwin, D. M. 1993. Aves. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 717–737. Chapman & Hall: London.
[WSZ18] Wang, M., T. A. Stidham & Z. Zhou. 2018. A new clade of basal Early Cretaceous pygostylian birds and developmental plasticity of the avian shoulder girdle. Proceedings of the National Academy of Sciences of the USA 115 (42): 10708–10713.
[ZZ01] Zhang F., Zhou Z., Hou L. & Gu G. 2001. Early diversification of birds: evidence from a new opposite bird. Chinese Science Bulletin 46 (11): 945–949.