Of the two existing generic representatives of the Camelidae (as the family in which they are both included is named), the Old World camels (Camelus) are characterized by their great bodily size, and the presence of one or two fleshy humps, which diminish or increase in size according to the physical condition of the animals themselves.
Although the name llama properly applies only to one of the domesticated breeds, zoologically it is taken to include all the South American representatives of the Camelidae, which form the genus Lama.
It is not easy to point out the characters in which the family approximates to the Camelidae, and only its general characteristics can be indicated.
The earliest representatives of the Tylopoda according to Professor Scott is the Middle Eocene genus Homacodon, typifying the family Homacodontidae, which is regarded as the common ancestor of both Camelidae and Oreodontidae, with resemblances to the European Oligocene genus Dichobune (see Artiodactyla).
Vii.; "The Extinct Camelidae of North America (1898), ibid., vol.
Vicugna), belonging to the Camelidae, with the structure and habits of the African camel, but smaller, having no hump, and inhabiting a mountainous and not a level sandy region.