Parker recognizes five genera, with about twenty species, which he combines into three sub-families: Dinornithinae with Dinornis, Anomalopteryginae with Pachyornis, Mesopteryx and Anomalopteryx, comprising the comparatively least specialized forms; and Emeinae with the genus Emeus, not to be confounded with the vernacular emeu.
The moas ranged in size from that of a turkey to truly colossal dimensions, the giant being Dinornis maximus, which, with a tibial length of 39 in., stood with its small head about 12 ft.
A diagnosis covering all the Ratitae (struthio, rhea, casuarius, dromaeus, apteryx and the allied fossils dinornis and aepyornis) would be as follows - (i) terrestrial birds without keel to the sternum, absolutely flightless; (ii) quadrate bone with a single proximal articulating knob; (iii) coracoid and scapula fused together and forming an open angle; (iv) normally without a pygostyle; (v) with an incisura ischiadica; (vi) rhamphotheca compound; (vii) without apteria or bare spaces in the plumage; (viii) with a complete copulatory organ, moved by skeletal muscles.
Fiirbringer, however, separated Apteryx with Dinornis from the rest, combining his "Apteryges" with Crypturi and Ga Ili as Alectorornithes, the latter being practically A.
Dinornis, numerous species, recently extinct, New Zealand.