Ornithothoraces

Ornithothoracines Temporal range: Early Cretaceous–Recent, 131–0Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of a juvenile enantiornithe (Liaoxiornis delicatus)
Southern ground hornbill (Bucorvus leadbeateri)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Pygostylia
Clade:	Ornithothoraces Chiappe & Calvo, 1994
Subgroups
†Enantiornithes Euornithes
Synonyms
Aerialae? Ji & Ji, 2001

Ornithothoraces is a clade of avialans that includes all enantiornithines ("opposite birds") and modern birds.

The name Ornithothoraces means "bird thoraxes". This refers to a modern, highly derived, anatomy of the thorax that has given the ornithothoracines superior flight capability compared to more primitive avialans. 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 131 million years ago,^[1] though at least one other enantiornithine, Noguerornis, may be even older, at up to 145.5 million years ago, though its exact age is uncertain.^[2]

Classification

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.^[3] In 1994, Chiappe and Calvo forwarded a phylogenetic definition of Ornithothoraces as the common ancestor of Iberomesornis romerali and modern birds, plus all their descendants.^[4] This was followed by Chiappe in 1996.^[5] This definition gives a node-based clade.

Sereno (1998)^[6] defined Ornithothoraces in the same node-based way, but used Sinornis santensis instead of Iberomesornis.

Cladogram following the results of a phylogenetic study by Lefèvre et al., 2014:^[7]

References