DIET AND CLIMATE OF THE LATE MIOCENE TELEOCERAS FOSSIGER FROM WESTERN CENTRAL KANSAS: EVIDENCE FROM STABLE C & O ISOTOPE ANALYSES OF TOOTH ENAMEL SAMPLES

Teleoceras fossiger was a Late Miocene rhinoceros from the High Plains of North America, with a North American Land Mammal Age (NALMA) of Early Hemphillian. Housed at the Sternberg Museum of Natural History (FHSM), the six molars of T. fossiger selected for this study were from the Ash Hollow Formation of two quarries in western central Kansas: the Minium Quarry in Graham County and a second quarry in Ellis County. Stable carbon and oxygen isotope analyses have been carried out on eighty-five serial tooth enamel samples obtained from these molars to reconstruct the diet of this rhino and the climate it lived in.

All the δ¹³C values of structural carbonate in the tooth enamel samples were less than -7‰ (vs. VPDB; with two samples between -7 and -8‰, 11 samples between -8 and -9‰, and all else less than -9‰). This means that: (1) if the western central Kansas were under water-stressed conditions, there would be very little (if any) C4 components in T. fossiger’s diet; or (2) if the western central Kansas were under normal conditions without water or other stresses, then T. fossiger may have consumed up to ~40% C4 vegetation. It is also worth noting that the intra-tooth variations in δ¹³C values were small (with the maximum being 2.0‰), which could well be the result of changing water availability or other conditions, rather than the presence of C4 plants. Taken together, C4 plants were less than ~10% in T. fossiger’s diet (and the local ecosystem if sampled proportionally), largely consistent with previous results.

The δ¹⁸O values were mostly greater than ~-4‰ (vs. VPDB), and vary only in a small range (up to ~2.7‰, compare to ~9‰ in modern day central Inner Mongolia at similar latitudes). Moreover, the inverse relationship between δ¹³C and δ¹⁸O values due to monsoon effect was only partly observed in our samples. This means that our study area was not under strong monsoon influence during the Late Miocene.