Master's Theses

Document Type

Thesis - campus only access

Date of Award

Fall 1992

Degree Name

Master of Science (MS)

Department

Geosciences

Advisor

Richard Zawerksi

Abstract

Aphelops was a hornless, cursorial, browsing, rhinoceros that lived in herds and was distinct morphologically and ecologically from the other North American Miocene rhinoceroses, Teleoceras and Peraceras. Measurements of presumptive male and female jaws show that Aphelops, like the modern Indian rhinoceros (Rhinoceros), was sexually dimorphic in tusk and diastemal size, but not in body size. The relative shape of the occipital condyles indicates that Aphelops was more active than Teleoceras, Peraceras, any of the extant rhinoceroses, or the hippopotamus. Cranial comparisons among Aphelops and the proboscis-bearing tapir (Tapirus) indicate that the former lacked a proboscis. However, Aphelops was a prehensile-lipped browser as evidenced by size and retraction of the narial notch, size of the infraorbital foramen, and relative brachydonty. Measurements of long bones show the possibility that later Aphelops were becoming more cursorial. Restorations of the face and body of Aphelops and its contemporaries are provided to supplement the above comparisons. Aphelops is comprised of three successive species that increased in size through the Miocene. Positions of the narial notch relative to the maxillary teeth are particular to each species. Aphelops lived in small herds on the American savanna, was the most successful aceratherine, and was one of the last American rhinoceroses to become extinct. Extinction of Apllelops resulted from the inability of it and other large browsing, non- ruminating herbivores to adapt to an increasingly continental climate.

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Rights

© 1992 David Wilcots

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