Mandibular osteopathy in a Hagerman horse, Equus simplicidens (Equidae, Mammalia), from Hagerman Fossil Beds National Monument (Idaho, USA)

Multimodality imaging, including computed tomography (CT) and digital radiography, was utilized to examine a fossilized hemimandible of a probable female Hagerman horse (Equus simplicidens) with a large, ventrally located, osseous deformation. Utilizing comparative pathology to the modern day horse, it was determined that the most likely etiology of the pathologic bony swelling along the ventral hemimandible was abnormal tooth development that led to chronic osteomyelitis and subsequent osseous proliferation, sclerosis and deformation.