Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
   Pygostylia Chatterjee 1997 [Chiappe 2001]
     Ornithothoraces Chiappe 1995
       Subclass Ornithuromorpha Chiappe, 2002 see Clade Ornithuromorpha Chiappe 2001
         1 Genus †Patagopteryx Alvarenga & Bonaparte, 1992
         2.1 Family †Hongshanornithidae O'Connor, Gao & Chiappe, 2010
         2.2.1 Genus †Yanornis Zhou & Zhang, 2001
         2.2.2.1 Genus †Yixianornis Zhou & Zhang, 2001
         2.2.2.2.1 Genus †Gansus Hou & Liu, 1984
         2.2.2.2.2.1 Genus †Apsaravis Norell & Clarke, 2001
         2.2.2.2.2.2 Ornithurae Haeckel 1866 [Gauthier 1986] {Chiappe 1991}