For this week's Fossil Friday we'll return to camels, specifically the large extinct camel Camelops hesternus that's pretty common in Pleistocene deposits in California.This specimen is an upper molar collected near the west dam of Diamond Valley Lake. I'm pretty sure this is the upper right first molar, although I can't yet rule out the possibility that it's the second molar. This tooth was found associated with several other molars and premolars, as well as small skull fragments that all appear to be from one individual.The image above is in occlusal view, showing the chewing surface. The tooth is fairly heavily worn, showing the pattern of folded enamel ridges; the shiny grayish-white ridges are enamel, with softer dentine in between. By having these alternating areas of hard enamel and softer dentine, the enamel ridges always stick out slightly beyond the occlusal surface, so the tooth maintains a sharp chewing surface even as it's being worn down. The elevated enamel ridges are especially noticeable in lingual view (since this is an upper tooth, the occlusal surface is at the bottom):
The particular pattern of enamel ridges is one of the primary means of distinguishing between different groups of mammals, even down to individual species. For some species it's possible to make an identification on the basis of a single well-preserved tooth.Camels have a general tooth pattern that's called selenodont, in reference to the crescent-shaped enamel ridges in occlusal view. Camels share the selenodont pattern with many of the camel's artiodactyl relatives, including cervids (deer) and bovids (bison, cows, antelopes, etc.).Just for the sake of completeness, here's the labial view of the same tooth:
