Ok, so while I slowly prepare a more lengthy post. Here’s the answer from last post. The skull I showed last time is that of a species of Metaxytherium, exactly which one, well, I’ll talk about that in the future. That skull is from Early Oligocene deposits, therefore it is several million years older than other reported species of Metaxytherium.
Here’s the skull in lateral and dorsal views. (Notice that part of the rostrum is missing.)It is somewhat similar to M. crataegense (=M. calvertense [Aranda-Manteca et al., 1994]) from the Early Miocene of the Western Atlantic and Caribbean, as well as to other species of Metaxytherium, but, it also displays plesiomorphic conditions not seen in those other species.
Another possibility would be Caribosiren turneri (drawing above modified from Reinhart, 1959), from the Early Oligocene of Puerto Rico. But, unlike Caribosiren the rostrum of this critter doesn’t seem to have been as extremely downturned; also it belonged to an animal at least 15% larger than Caribosiren. Other Oligocene halitheriines such as Halitherium schinzii from the European Early Oligocene, have different morphology of the parietal as well as much larger nasals; Eosiren imenti, known from the Early Oligocene of Egypt (Domning et al., 1994), is even more primitive than Halitherium schinzii, as it still has permanents premolars and canines, among other characteristics.
So, as far as I can tell, it seems to be a primitive Metaxytherium. There are other skulls from Early or Late Oligocene of the western Atlantic, which are very similar to this one, possibly the same species, that’s one thing I have to figure out as part of my thesis. If you’re going to the SVP meeting this year, you might learn more about this critter.
Aranda-Manteca, F. J., D. P. Domning and L. G. Barnes. 1994. A new Middle Miocene sirenian of the genus Metaxytherium from Baja California: relationships and paleobiogeographic implications. Proceedings of the San Diego Society of Natural History 29:191-204.
Domning, D. P., P. D. Gingerich, E. L. Simons and F. A. Ankel-Simons. 1994. A new Early Oligocene dugongid (Mammalia, Sirenia) from Fayum Province, Egypt. Contributions from the Museum of Paleontology, the University of Michigan 29(4):89-108.
Reinhart, R. H. 1959. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences 36(1):1-146.