Free US Law Dictionary

Ratites

Struthionidae (ostriches)
Rheidae (rheas)
Casuariidae (emus etc.)
†Aepyornithidae (elephant birds)
†Dinornithidae (moa)
Apterygidae (kiwis)

A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum - hence their name which comes from the Latin (ratis) for raft. Without this to anchor their wing muscles they could not fly even if they were to develop suitable wings.

Most parts of the former Gondwana have ratites, or have had until the fairly recent past. Their closest living relatives are the tinamous of South America.[1][2]