STABLE ISOTOPIC ANALYSES OF TEETH FROM FOUR GENERA OF HERBIVORES FROM THE LATE PLEISTOCENE OF SOUTHERN NEVADA

To address questions of diet within the Pleistocene fauna of Southern Nevada, we conducted delta¹³C and delta¹⁸O analyses of teeth from Mammuthus, Equus, Bison, and Camelops collected at the Gilcrease spring mound in northern Las Vegas Valley. Enamel from each tooth was serially sampled along the growth axis of the tooth. Five teeth from each genus were sampled and analyzed. Radiocarbon dates on mammoth teeth from this site constrain the age of these fossils to approximately 14 ka to 18 ka. This age range, together with the diverse megafauna, indicates that the deposit is correlative with Unit E1 of the Tule Springs area, several km to the east.

Intratooth variation is approximately 1-2 per mil among the three grazing taxa, and 3-4 per mil in Camelops. Subannual variation is recorded in some of the teeth. The carbon isotopic values from the three grazing taxa indicate that these animals consumed C₃ and C₄ grasses in the naturally occurring proportion, which was dominated by C₃ grasses. However, carbon isotopic values from Camelops teeth indicate a high proportion of C₄ vegetation in the diet. Independent vegetation records, paired with paleoclimatological reconstructions, indicate a low abundance of C₄ grasses during the interval of time in which these animals lived, but the halophytic C₄ shrub Atriplex is inferred to have been moderately abundant. Modern camelids in Asia prefer halophytic plants, including those of the genus Atriplex. These results suggest that Camelops individuals similarly consumed a high proportion of C₄ shrubs, probably including Atriplex, and that their diet varied seasonally.