Research Training Program

Chad Schennum
Virginia Tech
Blacksburg, Virginia

Robert Emry, Ph.D.
Supervising Scientist
Department of Paleobiology

"Could this experience have been any more perfect for me? My project consisted of doing exactly what I want to do in the future - working with fossils and using them for comparative morphology studies. How else would I rather spend my summer?!"

Brontotheres, an extinct family of mammals, have typically been reconstructed like a rhinoceros in size and body proportions, because those for which fossil skeletons are well known have body proportions much like those of rhinos. However, field observations while collecting skeletons of Protitan in Kazakhstan suggested that this genus of brontothere has exceptionally short limbs and long ribs, and might have adopted an amphibious lifestyle, becoming much like the hippopotamus. Similar adaptation is known to have occurred in another closely related mammal family, the Rhinocerotidae; Teleoceras, an extinct rhino that lived in North America about twenty million years ago, evolved body proportions similar to those of hippos, and became an ecological vicar of the hippo, adopting an amphibious lifestyle. In this study, limb proportions of Protitan were compared with those of three other genera of brontotheres, two genera of living rhinos, the extinct woolly-rhinoceros, the hippo-like rhino Teleoceras, and the hippo. The results were both expected and surprising. Protitan has shorter arm proportions than the hippo, but it turns out that Rhinotitan has longer arm proportions than the rhino. The comparison of arm proportions produces a well-defined range of data, showing that on the scale of hippo-like to rhino-like, brontotheres range from shorter than hippos to taller and more rangy than rhinos. Comparing leg proportions, though, does not produce the same results - the data range shows little definition. This has led to the hypothesis that perhaps proportional change in the leg is less critical than in the arm, due to how the limbs function with respect to the underside of the body.