Euornithes

Superregnum: Eukaryota
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Cladus: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Classis: Reptilia
Cladus: Eureptilia
Cladus: Romeriida
Subclassis: Diapsida
Cladus: Sauria
Infraclassis: Archosauromorpha
Cladus: Crurotarsi
Divisio: Archosauria
Subsectio: Ornithodira
Subtaxon: Dinosauromorpha
Cladus: Dinosauria
Ordo: Saurischia
Cladus: Theropoda
Cladus: Neotheropoda
Infraclassis: Aves
Cladus: Euavialae
Cladus: Avebrevicauda
Cladus: Pygostylia
Cladus: Ornithothoraces
Cladus: Euornithes
Ordines: †Chaoyangornithiformes - Ornithuromorpha
Name
Euornithes Cope, 1889

Euornithes (from Greek ευόρνιθες euórnithes meaning "true birds") is a natural group which includes the most recent common ancestor of all avialans closer to modern birds than to Sinornis.

Description

Clarke et al. (2006) found that the most primitive known euornithians (the Yanornithiformes) had a mosaic of advanced and primitive features. These species 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 showed only paired plumes or a tuft of short feathers.[2]
Classification

The name Euornithes has been used for a wide variety of avialan 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 animals closer to birds than to Enantiornithes (represented by Sinornis). This definition currently includes similar 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, Ornithuromorpha is a slightly less inclusive group.
Relationships

The cladogram below follows the results of a phylogenetic analysis by Lee et al., 2014:[3]

Ornithothoraces	†Enantiornithes   Euornithes   †Archaeorhynchus       †Jianchangornis       †Zhongjianornis       †Chaoyangia       †Schizooura   Ornithuromorpha     †Patagopteryx     †Vorona         †Ambiortus       †Songlingornithidae       †Hongshanornithidae       †Apsaravis       †Gansus       †Hollanda   Ornithurae   †Ichthyornis       †Hesperornithes       †Limenavis     Aves (modern birds)

 
Other genera

The following is a list of primitive euornithian genera and those that cannot be confidently referred to any subgroups, following Holtz (2011) unless otherwise noted.[4]

†Alamitornis
†Changmaornis[5]
†Changzuiornis[6]
†Dingavis[6]
†Gargantuavis
†Horezmavis
†Iteravis[6]
†Juehuaornis[6]
†Platanavis
†Wyleyia?
†Yumenornis[5]
†Xinghaiornis[6]
†Zhyraornis

Note that Holtz also included the genera Eurolimnornis and Piksi as euornitheans, though they have since been re-identified as pterosaurs.[7]
References

Min Wang; Xiaoting Zheng; Jingmai K. O’Connor; Graeme T. Lloyd; Xiaoli Wang; Yan Wang; Xiaomei Zhang; Zhonghe Zhou (2015). "The oldest record of Ornithuromorpha from the Early Cretaceous of China". Nature Communications. 6: Article number 6987. doi:10.1038/ncomms7987. PMC 5426517. PMID 25942493.
Clarke, Julia A.; Zhou, Zhonghe; Zhang, Fucheng (2006). "Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of Yixianornis grabaui". Journal of Anatomy. 208 (3): 287–308. doi:10.1111/j.1469-7580.2006.00534.x. PMC 2100246. PMID 16533313.
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. 63 (3): 442–9. doi:10.1093/sysbio/syt110. PMID 24449041.
Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
Wang, Y.-M.; et al. (2013). "Previously Unrecognized Ornithuromorph Bird Diversity in the Early Cretaceous Changma Basin, Gansu Province, Northwestern China". PLoS ONE. 8 (10): e77693. doi:10.1371/journal.pone.0077693. PMC 3795672. PMID 24147058.
Huang, J., Wang, X., Hu, Y., Liu, J., Peteya, J. A., & Clarke, J. A. (2016). A new ornithurine from the Early Cretaceous of China sheds light on the evolution of early ecological and cranial diversity in birds. PeerJ, 4: e1765. doi:10.7717/peerj.1765
Federico L. Agnolin; David Varricchio (2012). "Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird". Geodiversitas. 34 (4): 883–894. doi:10.5252/g2012n4a10. Archived from the original on 2013-01-07.