Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
   Subclass Ornithurae Haeckel, 1866 see Clade Ornithurae Haeckel 1866 [Gauthier 1986] {Chiappe 1991}
     1 Order †Liaoningornithiformes Hou, 1996
     2 Order †Chaoyangornithiformes Hou, 1997, nom. imperf. see Order Chaoyangiiformes Hou, 1997
     3 Order †Yanornithiformes Zhou & Zhang, 2001
     4 Order †Yixianornithiformes Zhou & Zhang, 2006
     5 Order †Gansuiornithiformes nom. imperf. see Order Gansuiformes Hou & Liu, 1984