PALEOECOLOGY OF THE ENIGMATIC RHINOCEROS CHILOTHERIUM IN CENTRAL ASIA

We report a new occurrence of the rhinocerotid Chilotherium in the Kochkor basin in Kyrgyzstan. While some geologic reports refer to Chilotherium in Kyrgyzstan, no described material exists from the country and all published material is now lost to science. Therefore, our new material is important for not only recognizing the occurrence of the genus, but also understanding the evolution, ecology, and dispersion of various fossil taxa including Chilotherium. Few studies have examined the global distribution of Chilotherium. While a not uncommon taxon, we found that 84% of Chilotherium specimens were found in China, mostly from the Linxia Basin. Thus, the Kyrgyz specimens represent an important geographic extension of the taxon, and may clarify the relationship between ecology and species diversity.

Of collected fossils from Kyrgyzstan, Chilotherium is the most abundant taxon. A species level diagnosis of Chilotherium is difficult because the taxonomy poorly constrained. There are only three valid species (C. anderssoni, C. haberi, C. kiliasi) but close to 20 published species. By mapping occurrences globally, we hope to clarify taxonomic relationships as well as to assign the new Kyrgyz material to a species level.

The Kyrgyz fossils are found with Dorcas dorcadoides, Sivatherium, Hipparion , and a tortoise. These taxa are associated with open ecologies. The astragalus of the new Chilotherium fossils is most similar to the North American Teloceras, a large barrel bodied rhino with short legs. We therefore suggest that Chilotherium was less cursorial than several contemporaneous rhino taxa in Asia. Also, our database of Chilotherium occurrences only reports localities above 2,000m elevation. While paleoaltitudes may be different than modern altitudes, recent studies support the construction of both the Himalayan and Tien Shan ranges prior to the late Mio/Pliocene. This indicates that Chilotherium occupied a different ecological niche.