The English used in this article or section may not be easy for everybody to understand. (November 2011)
Paleognath is a word derived from the ancient Greek for "old jaws" in reference to the skeletal anatomy of the palate, which is described as more primitive and reptilian than that in other birds. Paleognathous birds are uncontroversially the most primitive, or basal, living birds, though there is some controversy about the precise relationship between them and the other birds.
The order Tinamiformes (tinamous) includes nine living genera and forty-seven species.
The Apterygiformes (kiwis) include five species in one genus (Apteryx).
The Rheiformes (rheas) have two genera with one species each.
The Struthioniformes (ostriches) have only one living species.
There are extinct orders: the Lithornithiformes, the Dinornithiformes (moas), and the Aepyornithiformes (elephant birds). There are other extinct orders which have been allied with the Palaeognathae by at least one author, but their affinities are a matter of dispute: the Ambiornithiformes, the Gansuiformes, the Paleocursornithiformes, the Gobipterygidae.
These are the families of running-birds: