genera of mammals weighing over became extinct. Isotope analysis can be used to identify some chemical elements, allowing researchers to make inferences about the diet of the species found in the pits. Isotope analysis of bone collagen extracted from LaBrea specimens provides evidence that the dire wolf, Smilodon, and the American lion (Panthera atrox) competed for the same prey. Their prey included "yesterday's camel" (Camelops hesternus), the Pleistocene bison (Bison antiquus), the "dwarf" pronghorn (Capromeryx minor), the western horse (Equus occidentalis), and the "grazing" ground sloth (Paramylodon harlani) native to North American grasslands. The Columbian mammoth (Mammuthus columbi) and the American mastodon (Mammut americanum) were rare at LaBrea. The horses remained mixed feeders and the pronghorns mixed browsers, but at the Last Glacial Maximum and its associated shift in vegetation the camels and bison were forced to rely more heavily on conifers. A study of isotope data of La Brea dire wolf fossils dated 10,000YBP provides evidence that the horse was an important prey species at the time, and that sloth, mastodon, bison, and camel were less common in the dire wolf diet. This indicates that the dire wolf was not a prey specialist, and at the close of the Late Pleistocene before its extinction it was hunting or scavenging the most available herbivores. Dentition and bite force When compared with the dentition of genus Canis members, the dire wolf was considered the most evolutionary derived (advanced) wolf-like species in the Americas. The dire wolf could be identified separately from all other Canis species by its possession of: "P2 with a posterior cusplet; P3 with two posterior cusplets; M1 with a mestascylid, entocristed, entoconulid, and a transverse crest extending from the metaconid to the hyperconular shelf; M2 with entocristed and entoconulid." A study of the estimated bite force at the canine teeth of a large sample of living and fossil mammalian predators, when adjusted for the body mass, found that for placental mammals the bite force at the canines (in newtons/kilogram of body weight) was greatest in the dire wolf (163), followed among the modern canids by the four hypercarnivores that often prey on animals larger than themselves: the African hunting dog (142), the gray wolf (136), the dhole (112), and the dingo (108). The bite force at the carnassials showed a similar trend to the canines. A predator's largest prey size is strongly influenced by its biomechanical limits. The