Ornithothoraces

Ornithothoracines Temporal range: Early Cretaceous–Recent, 140–0 Ma PreЄ Є O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Node:	Pygostylia
Node:	Ornithothoraces Chiappe & Calvo, 1994
Subgroups
†Enantiornithes Ornithurae

Ornithothoraces is a clade of birds which includes all enantiornithines and modern birds (Neornithes).

The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax which gave the ornithothoracines superior flight capability compared to more primitive birds. This anatomy includes elongated coracoids, a large, keeled sternum, and modified glenoid joint of the shoulder, along with a semirigid dorsal rib cage. The earliest known member of the group is Protopteryx fengningensis, from the Sichakou Member of the Huajiying Formation of China, which dates to around 140 Ma ago.^[1]

Definition

Under older classifications, the primitive toothed members of the group was united in the superorder Odontognathae, which together with the Palaeognathae and Neognathae comprised the Neornithes.^[2] In 1994, Chiappe and Calvo forwarded a phylogenetic definition of Ornithothoraces as the common ancestor of Iberomesornis romerali and extant birds, plus all their descendants.^[3] This was followed by Chiappe in 1996.^[4] This definition gives a node-based clade.

Sereno (1998)^[5] defined Ornithothoraces in the same node-based way, but used Sinornis santensis instead of Iberomesornis.

References

1. ^ Jin, F.; Zhang, F.C.; Li, Z.H.; Zhang, J.Y.; Li, C.; Zhou, Z.H. (2008). "On the horizon of Protopteryx and the early vertebrate fossil assemblages of the Jehol Biota". Chinese Science Bulletin 53 (18): 2820–2827. doi:10.1007/s11434-008-0209-5. 
2. ^ Romer, A. S. & Parsons, T. S. (1985): The Vertebrate Body. (6th ed.) Saunders, Philadelphia.
3. ^ Chiappe, Luis; Calvo, J.O. (1994) "Nequenornis volans, a new Late Cretaceous bird (Enantiornithes:Avisauridae) from Patagonia, Argentina". Journal of Vertebrate Paleontology 14:230-246.
4. ^ Chiappe, Luis (1996). "Late Cretaceous birds of southern South America: anatomy and systematics of Enantiornithes and Patagopteryx deferrariisi". pp. 203-244 in G. Arratia (ed.), Contributions of Southern South America to Vertebrate Paleontology. Munchner Geowissenschaftliche Abhandlungen, reihe A, Geologieund Palaontologie 30. Verlag Dr. Friedrich Pfeil, Munich.
5. ^ Sereno, Paul (1998). "A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria". Neues Jahrbuch fur Geologie und Palaontologie 210:41-83.