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Ratite

A ratite is any of a diverse group of large, flightless birds of Gondwanian origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their breastbone and, lacking a strong anchor for their wing muscles, could not fly even were they to develop suitable wings.

Most parts of the former Gondwana have ratites, or have had until the fairly recent past.

The traditional account of ratite evolution has the order emerging in Gondwana in cretaceous times, then evolving in their separate directions as the continents drifted apart. Cladistic evidence for this is strong: ratites share too many features for their current forms to be easily explained by convergent evolution. However, recent analysis of genetic variations between the ratites conflict with this: DNA analysis appears to show that the ratites diverged from one another too recently to share a common Gondwanian ancestor, and suggest that the kiwis are more closely related to the cassowaries than the moa! At present there is no generally accepted explanation. Research continues.