| Popis: |
A new skull of Desmostylus hesperus Marsh, 1888 is described from the late Middle Miocene Tachikaraushinai Formation, Utanobori, Hokkaido, northern Japan. The specimen, GSJ-F7745, is a nearly complete skull and mandible, but the posterior halves of their left sides are missing. It was a juvenile individual, having part of the worn fourth deciduous molar (dp4) in the right upper jaw. Another specimen (GSJ-F7743) was uncovered in the same formation near the same area where GSJ-F7745 was collected. Both fossils represent nearly the same ontogenetic stage and were of the same gender. There are two different opinions regarding the position of the external acoustic meatus of Desmostylus. The cranial cavity of specimen GSJ-7745 is observable and reveals that the meatus should be identified as being the foramen on the lateral surface of the posterior portion of the zygomatic arch. |
