The holotype of the younger species "O. leptodon" was found with both tusks "in situ", the right one long, the erupted portion , the left tusk was only but a wear facet indicates that it was erupted. The skull of "O. leptodon" differs from that of "O. peruvianus" in the absence of a premaxillary foramina and the presence of a dorsal fossa (shallow depression) on the premaxilla. This fossa suggests the presence of a melon in "O. leptodon", an organ either absent or strongly reduced in "O. peruvianus". On the other hand, the orbit in "O. leptodon" has an anterior edge that is only slightly concave, whereas it is deeply notched in "O. peruvianus" which suggests that "O. peruvianus" used binocular vision.