Ornithuromorpha

Euornithians Temporal range: Early Cretaceous–Recent,
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Clade:	Avialae
Clade:	Pygostylia
Clade:	Ornithothoraces
Clade:	Euornithes Cope, 1889
Subgroups
†Ambiortiformes †Archaeorhynchus †Chaoyangiformes †Eurolimnornithiformes †Gargantuavis †Holbotia †Hollanda †Hongshanornithidae †Horezmavis †Hulsanpes? †Jianchangornis Ornithurae †Patagopterygiformes †Piksi †Platanavis †Schizooura †Vorona? †Wyleyia? †Yanornithiformes †Zhyraornithi
Synonyms
Ornithuromorpha Chiappe et al., 1999

Euornithians (meaning "true birds" in Greek) is the name of a natural group which includes the most recent common ancestor of all birds closer to modern birds than to Sinornis.

Description

Clarke at al. (2006) found that the most primitive known euornithians (the Yanornithiformes) had a mosaic of advanced and primitive features. These birds retained primitive features like gastralia (belly ribs) and a pubic symphysis. They also showed the first fully modern pygostyles, and the type specimen of Yixianornis (IVPP 13631) preserves eight elongated rectrices (tail feathers) in a modern arrangement. No earlier pygostylians are known which preserve a fan of tail feathers of this sort; instead, they show only paired plumes or a tuft of short feathers.

Classification

The name Euornithes has been used for a wide variety of bird groups since it was first named by Edward Drinker Cope in 1889. It was first defined as a clade in 1998 by Paul Sereno, who made it the group of all birds closer to living birds than to Enantiornithes (represented by Sinornis). This definition currently includes the same content as another widely-used name, Ornithuromorpha, named and defined by Luis Chiappe in 1999 as the common ancestor of Patagopteryx, vorona, and Ornithurae, plus all of its descendants. Because one definition is node-based and the other branch-based, it is likely that they were not the same group in reality. However, because no non-ornithuromorph euornithians are currently known, they are usually treated as synonyms.