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
         Family †Hongshanornithidae O'Connor, Gao & Chiappe, 2010
           1 Genus †Longicrusavis O'Connor, Gao & Chiappe, 2010
           2 Genus †Hongshanornis Zhou & Zhang, 2005