Description: The Rhonoceraids are divided into two groups: the cursorial (running) Hyracodontidae, the aquatic Amnyodontidae, and the true rhinoceroses Rhinoceratidae. The first two groups are known only from fossils while there are several true rhinos found in Africa and Asia today. This is a molar from the maxilla (upper jaw) of Hyracodon nebrascensis complete with root showing in the matrix. It was found by avocational paleontologist Frank Garcia back in 1980. The morphology is quite similar to that of rhinos today, albeit at much smaller size given this species was about the same dimensions as a modern-day sheep. See my other offerings from a complete pathological mandible of this same taxon.