Phylum Chordata Bateson, 1885 - chordates
   Subphylum Vertebrata Cuvier, 1812 - vertebrates
     Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
       Order †Aepyornithiformes Newton, 1884
       Order †Alexornithiformes Brodkorb, 1976
       Order †Ambiortiformes Kurochkin, 1982
       Order †Archaeopterygiformes Fürbringer, 1888
       Order †Cathayornithiformes Zhou, Jin & Zhang, 1992
       Order †Diatrymiformes Shufeldt, 1913
       Order †Dinornithiformes Gadow, 1893 - moas
       Order †Enantiornithiformes Martin, 1983 see Order Alexornithiformes Brodkorb, 1976
       Order †Gansuiformes Hou & Liu, 1984
       Order †Gobipterygiformes Elzanowski, 1974 see Order Alexornithiformes Brodkorb, 1976
       Order †Hesperornithiformes Fürbringer, 1888
       Order †Iberomesornithiformes Sanz & Bonaparte, 1992
       Order †Ichthyornithiformes Marsh, 1873
       Order †Limnornithiformes Kessler & Jurcsák, 1984, nom. illeg.
       Order †Lithornithiformes Houde, 1988
       Order †Palaeocursornithiformes Kessler & Jurcsák, 1986
       Order †Patagopterygiformes Alvarenga & Bonaparte, 1992
       Order †Praeornithiformes Rautian, 1978
       Order †Protoaviformes Chatterjee, 1991, nom. dub.
       Order †Sandcoleiformes Houde & Olson, 1992
       01 Order Struthioniformes Latham, 1790
       02 Order Rheiformes Forbes, 1884 see Suborder Rheae Forbes, 1884
       03 Order Casuariiformes Sclater, 1880
       04 Order Apterygiformes Haeckel, 1866
       05 Order Tinamiformes Huxley, 1872
       06 Order Sphenisciformes Sharpe, 1891
       07 Order Gaviiformes Wetmore & Miller, 1926
       08 Order Podicipediformes Fürbringer, 1888
       09 Order Procellariiformes Fürbringer, 1888
       10 Order Pelecaniformes Sharpe, 1891
       11 Order Ciconiiformes Bonaparte, 1854
       12 Order Anseriformes Wagler, 1831 - waterfowl and screamers
       13 Order Falconiformes Sharpe, 1874
       14 Order Galliformes Temminck, 1820 - fowl
       15 Order Gruiformes Bonaparte, 1854
       16 Order Charadriiformes Huxley, 1867 - shorebirds, gulls, auks
       17 Order Columbiformes Latham, 1790 - pigeons and allies
       18 Order Psittaciformes Wagler, 1830 - parrots
       19 Order Cuculiformes Wagler, 1830 - cuckoos and plantain-eaters
       20 Order Strigiformes Wagler, 1830 - owls
       21 Order Caprimulgiformes Ridgway, 1881 - nightjars
       22 Order Apodiformes Peters, 1940 - swifts
       23 Order Coliiformes Murie, 1872 - mousebirds
       24 Order Trogoniformes Wetmore & Miller, 1926 - trogons
       25 Order Coraciiformes Forbes, 1884 - rollerlike birds
       26 Order Piciformes Meyer & Wolf, 1810 - scansorial birds
       27 Order Passeriformes Linnaeus, 1758