Abstract
The hypothesis that giant short-faced bears of the genera Agriotherium and Arctodus were primarily carnivorous and preyed on large terrestrial mammals is examined. It is argued that the shape and wear pattern of the cheek teeth and the presence of the premasseteric fossa on the mandible in these two ursids suggest a large amount of plant material in their diet. Likewise, the absence of adaptations for either ambush or pursuit predation in their skull and postcranial skeleton suggest that they did not prey on large terrestrial mammals. Further support for this conclusion is provided by a comparison of the dental and skeletal morphology of Agriotherium and Arctodus to that of Hemicyon ursinus, an extinct ursid widely accepted to have been a predaceous carnivore. However, it is also argued that the giant short-faced bears included a large amount of animal material in their diets, which was obtained by scavenging.