organisms see Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
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   Eukaryota Chatton, 1925 - eukaryotes see Domain Eukaryota Chatton, 1925
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     Kingdom Animalia Linnaeus, 1758 - animals
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       Deuterostomia Grobben, 1908 - deuterostomes see Infrakingdom Deuterostomia Grobben, 1908
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         Phylum Chordata Bateson, 1885 - chordates
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           Subphylum Vertebrata Cuvier, 1812 - vertebrates see Infraphylum Vertebrata Lamarck, 1801
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             Superclass Tetrapoda Goodrich, 1930 - tetrapods see Clade Tetrapoda Hatschek & Cori 1896 [Gauthier, Kluge & Rowe 1988], nom. cl. inval.
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               Class Aves Linnaeus, 1758 - birds see Subclass Aves Linnaeus, 1758
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                 Subclass Neornithes Gadow, 1893 see Clade Neornithes Gadow, 1893
                Count: [*] 27o1f6g16s; †5o
                   01 Order Tinamiformes Huxley, 1872
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                   02 Order †Palaeocursornithiformes Kessler & Jurcsák, 1986
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                   03 Order Struthioniformes Latham, 1790
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                   04 Order Rheiformes Forbes, 1884 see Suborder Rheae Forbes, 1884
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                   05 Order Casuariiformes Sclater, 1880
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                   06 Order †Dinornithiformes Gadow, 1893 - moas
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                   07 Order †Aepyornithiformes Newton, 1884
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                   08 Order Apterygiformes Haeckel, 1866
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                   09 Order Galliformes Temminck, 1820 - fowl
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                   10 Order Anseriformes Wagler, 1831 - waterfowl and screamers
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                   11 Order Strigiformes Wagler, 1830 - owls
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                   12 Order Coraciiformes Forbes, 1884 - rollerlike birds
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                   13 Order †Sandcoleiformes Houde & Olson, 1992
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                   14 Order Coliiformes Murie, 1872 - mousebirds
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                   15 Order Piciformes Meyer & Wolf, 1810 - scansorial birds
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                   16 Order Passeriformes Linnaeus, 1758
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                   17 Order Apodiformes Peters, 1940 - swifts
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                   18 Order Caprimulgiformes Ridgway, 1881 - nightjars
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                   19 Order Trogoniformes Wetmore & Miller, 1926 - trogons
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                   20 Order Cuculiformes Wagler, 1830 - cuckoos and plantain-eaters
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                   21 Order Psittaciformes Wagler, 1830 - parrots
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                   22 Order †Diatrymiformes Shufeldt, 1913
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                   23 Order Gruiformes Bonaparte, 1854
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                   24 Order Charadriiformes Huxley, 1867 - shorebirds, gulls, auks
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                   25 Order Columbiformes Latham, 1790 - pigeons and allies
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                   26 Order Falconiformes Sharpe, 1874
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                   27 Order Ciconiiformes Bonaparte, 1854
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                   28 Order Podicipediformes Fürbringer, 1888
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                   29 Order Pelecaniformes Sharpe, 1891
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                   30 Order Procellariiformes Fürbringer, 1888
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                   31 Order Sphenisciformes Sharpe, 1891
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                   32 Order Gaviiformes Wetmore & Miller, 1926
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