Ornithothoraces

Ornithothoracines
Temporal range:
Early CretaceousPresent, 131–0 Ma
Fossil of a juvenile enantiornithe (Liaoxiornis delicatus)
Southern ground hornbill (Bucorvus leadbeateri)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Order: Saurischia
Suborder: Theropoda
Clade: Pygostylia
Clade: Ornithothoraces
Chiappe & Calvo, 1994
Subgroups
Synonyms
  • Aerialae? Ji & Ji, 2001

Ornithothoraces is a group of avialans that includes all enantiornithines ("opposite birds") and the euornithes ("true birds"), which contains modern birds and their ancestors. The name Ornithothoraces means "bird thoraxes". This refers to the modern, highly advanced anatomy of the thorax that gave the ornithothoracines superior flight capability compared to more primitive avialans. This anatomy includes a large, keeled breastbone, elongated coracoids and a modified glenoid joint in the shoulder, and a semi-rigid rib cage.

The earliest known members of the group are the enantiornithes Protopteryx fengningensis and Eopengornis martini, as well as the euornithine Archaeornithura meemannae, all from the Sichakou Member of the Huajiying Formation in China, which has been dated to 130.7 million years old.[1] At least one other enantiornithine, Noguerornis gonzalezi, may be even older, at up to 145.5 million years ago, though its exact age is uncertain.[2]

Classification

In 1994, Chiappe and Calvo established a phylogenetic definition of the group. They defend Ornithothoraces as a node-based clade, the common ancestor of Iberomesornis romerali and modern birds, and all of its other descendants.[3] In 1998, Paul Sereno defined Ornithothoraces in the same way, but used Sinornis santensis instead of Iberomesornis romerali.[4]

The cladogram below follows the results of a phylogenetic analysis by Lee et al., 2014:[5]

Ornithothoraces

Enantiornithes


Euornithes

Archaeorhynchus




Jianchangornis




Zhongjianornis




Chaoyangia




Schizooura


Ornithuromorpha


Patagopteryx



Vorona





Ambiortus




Songlingornithidae




Hongshanornithidae




Apsaravis




Gansus




Hollanda


Ornithurae

Ichthyornis




Hesperornithes




Limenavis



Aves (modern birds)


















References

  1. Wang, M.; Zheng, X.; o’Connor, J. K.; Lloyd, G. T.; Wang, X.; Wang, Y.; Zhang, X.; Zhou, Z. (2015). "The oldest record of ornithuromorpha from the early cretaceous of China". Nature Communications 6: 6987. doi:10.1038/ncomms7987. PMID 25942493.
  2. Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  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. doi:10.1080/02724634.1994.10011554.
  4. 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.
  5. Lee, Michael SY; Cau, Andrea; Darren, Naish; Gareth J., Dyke (2013). "Morphological Clocks in Paleontology, and a Mid-Cretaceous Origin of Crown Aves". Systematic Biology (Oxford Journals) 63: 442–449. doi:10.1093/sysbio/syt110. PMID 24449041.
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