Oxydactylus of the Lower Miocene has the anterior teeth small recurved tusks, the vestiges of the lateral digits have disappeared or co-ossified, the median pair is more closely appressed and the size has increased to that of a llama or larger.
In Protolabis of the Middle Miocene the first and second upper incisors are reduced in size, the molar crowns are higher, and the metapodials are co-ossified to a varying degree in different species and at different ages. In Procamelus of the Upper Miocene the first and second upper incisors have disappeared, and the co ossification of the metapodials is complete. Another side branch, Alticamelus, in the later Miocene and Pliocene differs from Pro camelus in the long limbs and neck and relatively small head.
In the Pliocene follow a number of diverse genera incorrectly grouped under the name of Pliauchenia, and characterized by the loss of the second premolar in upper and lower jaw; but while they agree in this particular they differ widely in size, proportions, retention or loss of other teeth, height of molar crowns, etc. The best known is Megatylopus, probably identical with Para camelus of the Chinese Pliocene, larger and more robust than the modern camel, with f oot-pads less developed, but in most respects approximately ancestral. A group of smaller species, to which the name Pliauchenia may be found applicable, shows a similar approach to the llamas; a third group appears to be derived from Alticamelus, and a fourth parallels the Virginia deer in propor tions (although not related).
In the Pleistocene the genus Came/ops has lost the third lower premolar as well as pi-, and is much reduced ; pi-is present or absent in different species. It is of about the size and proportions
of the modern camels, but lacks the broadly flattened toes and probably had not much padding on the foot. Another genus, akin to the llamas but with longer cannon-bones, relatively smaller head and sometimes retaining occurs in the Pleistocene of the southern and south-western United States.
It has been generally believed that the camels became extinct in North America in the older Pleistocene, but recent evidence shows that some at least survived in Nevada until almost recent times, and probably elsewhere in the south and south-west until late Pleistocene. The splitting up of the family into the camels proper and the llama group is clearly foreshadowed in the geo graphical distribution of the Pliocene and Pleistocene species, many of the south-western species showing more affinities to the llamas, while those of the north-west are nearer to the camels. The Alaskan species and the Chinese Paracamelus make a still closer approach to the camel, and the Siwalik species is a typical Camelus. The Rumanian "Camelus" alutensis is, however, a side branch with low-crowned molars, slender jaw and retaining p, related to one of the North American Pliocene groups. In South America Palaeolama of the early Pleistocene, while retaining the second and third premolars like Procamelus, is quite llama-like in details of molar construction, in characters and proportions of skull and skeleton.