Osteoborus first appeared during the Late Miocene Epoch (about 8 million years ago), and became extinct by about 1.5 million years ago during the Pleistocene.  It was a genus of primitive dogs with robust, conical teeth quite similar to those of hyenas.  This kind of dentition is an adaptation to crushing bones.  In fact, the group of dogs to which this genus belongs is known as the borophagines(bone eaters).  Note the massively thickened enamel and stout build of the tooth shown in the second photo.  These dogs are believed to have not been active hunters, but primarily scavenging in habit.