Desmostylus was a large, hippopotamus-like creature, with the adult Keton specimen of D. hesperus measuring 275 cm (9.02 ft) in length, 105 cm (3.44 ft) in height and 1,283 kilograms (2,829 lb) in body mass; the largest known humerus, which is 1.3 times that of the Keton specimen in length, probably belonged to an individual with a mass of 2.8 metric tons (3.1 short tons).[3] It had a short tail and powerful legs with four hooves. The animal's jaws were elongated and sported forward-facing tusks, which were elongated canines and incisors.[4]
Most likely fully aquatic, Desmostylus is thought to have lived in shallow water in coastal regions, usually less than 30 meters deep.[5] Recent isotope work indicates that Desmostylus more likely lived (or spent a large amount of time) in freshwater or estuary ecosystems foraging for aquatic freshwater plants.[6]
Its less dense bone structure suggests that Desmostylus had a lifestyle of active swimming and possibly feeding at the surface, unlike other desmostylians that were primarily slow swimmers and/or bottom walkers and sea grass feeders.[7]
Species
Desmostylus hesperus (synonyms and invalid names: D. watasei, D. cymatias, D. californicus, D. mirabilis, D. minor, Desmostylella typica),[2]D. coalingensis (syn. Vanderhoofius coalingensis),[8][9] and D. japonicus.
Several other species were later described based on minor differences in tooth morphology. Most or all of these species have been synonymized with D. hesperus since variation in tooth morphology between individuals assigned to one of these species has proven to be to greater than the differences between species.[12]
Desmostylus japonicus was described by Yoshiwara & Iwasaki 1902 based on a well-preserved partial skull and named by Tokunaga & Iwasaki 1914. It has been reproposed as distinct species based on cranial morphology.[12]
^Inuzuka, N. (1996). Body size and mass estimates of desmostylians(Mammalia). The Journal of the Geological Society of Japan, 102(9), 816–819. https://doi.org/10.5575/geosoc.102.816
^Kumiko Matsui; Katsuo Sashida; Sachiko Agematsu; Naoki Kohno (2017). "Habitat preferences of the enigmatic Miocene tethythere Desmostylus and Paleoparadoxia (Desmostylia; Mammalia) inferred from the depositional depth of fossil occurrences in the Northwestern Pacific realm". Palaeogeography, Palaeoclimatology, Palaeoecology. 471: 254–265. doi:10.1016/j.palaeo.2017.02.005.
Inuzuka, Norihisa; Domning, Daryl P.; Ray, Clayton E. (1984). "Summary of taxa and morphological adaptations of the Desmostylia". Island Arc. 3 (4): 522–537. doi:10.1111/j.1440-1738.1994.tb00131.x.
Palmer, Douglas (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. ISBN1-84028-152-9. OCLC313633743.
Reinhart, Roy Herbert (1959). "A review of the Sirenia and Desmostylia". University of California Publications in Geological Sciences. 36 (1): 1–146. OCLC3474601.
