| Ornithothoracines | |
|---|---|
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| Fossil of an enantiornithean (Junornis houi) | |
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| Southern ground hornbill (Bucorvus leadbeateri) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Avialae |
| Clade: | Pygostylia |
| Clade: | Ornithothoraces Chiappe & Calvo, 1994 |
| Subgroups | |
Ornithothoraces is a group ofavialandinosaurs that includes allenantiornithes ("opposite birds") and theeuornithes ("true birds"), which includes modernbirds and their closest ancestors. The name Ornithothoraces means "bird thoraxes". This refers to the modern, highly advanced anatomy of thethorax that gave the ornithothoracines superior flight capability compared with more primitive avialans. This anatomy includes a large, keeled breastbone, elongatedcoracoids and a modifiedglenoid joint in the shoulder, and a semi-rigid rib cage. In spite of this at least the sternum seems to have developedconvergently rather than being a truehomology.[1]
The earliest known members of the group are the enantiornitheansProtopteryx fengningensis,Eopengornis martini, andCruralispennia multidonta, as well as the euornithineArchaeornithura meemannae, all from the Sichakou Member of theHuajiying Formation inChina, which has been dated to 130.7 million years old.[2] At least one other enantiornithean,Noguerornis gonzalezi, may be even older, at up to 145.5 million years ago, though its exact age is uncertain.[3]
In 1994, Chiappe and Calvo established aphylogenetic definition of the group. They defend Ornithothoraces as a node-basedclade, the common ancestor ofIberomesornis romerali and modern birds, and all of its other descendants.[4] In 1998,Paul Sereno defined Ornithothoraces in the same way, but usedSinornis santensis instead ofIberomesornis romerali.[5]
The cladogram below follows the results of a phylogenetic analysis by Wanget al., 2016:[6]
| Ornithothoraces | |
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