Ostriches, rheas and related birds are ratites - an order of flightless birds. The other members are the kiwis, emu, cassowary, as well as various extinct species such as the elephant bird.
Scientific name: Struthioniformes
The shading illustrates the diversity of this group - the darker the colour the greater the number of species. Data provided by WWF's Wildfinder.
Discover the other animals and plants that lived during the following geological time periods.
A ratite is any of a diverse group of large, flightless birds of the superorder Palaeognathae. There is still some controversy regarding the systematics involved. Some sources state that Ratites are synonymous with Struthioniformes, while other sources state that Ratites are the same group, only that the order Struthioniformes contains only the Ostrich and possibly the Elephant Bird. Ratites belong to the modern bird superorder Palaeognathae which consists of ratites and tinamous (compare to Neognathae). Unlike other flightless birds, the ratites have no keel on their sternum – hence the name 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 Supercontinent have ratites, or did have until the fairly recent past. Their closest living relatives are the tinamous of South America.
Some taxonomical systems consider the various families of ratites to be orders, but the system used here uses the order "Struthioniformes" to refer to all ratites.
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