Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct. Three species of elephant are recognized: the African bush elephant, the African forest elephant and the Indian or Asian elephant although some group the two African species into one and some researchers also postulate the existence of a fourth species in West Africa. All other species and genera of Elephantidae are extinct. Most have been extinct since the last ice age, although dwarf forms of mammoths might have survived as late as 2,000 BCE. Elephants and other Elephantidae were once classified with other thick-skinned animals in a now invalid order, Pachydermata.