# Desmostylus
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{{Short description|Extinct family of mammals}}
{{Automatic taxobox
| fossil_range = {{Fossil range|Oligocene|Miocene}}
| image = Desmostylus ROM.jpg
| image_caption = ''Desmostylus'', [Royal Ontario Museum](/source/Royal_Ontario_Museum)
| image2 = Desmostylus_3_NT.jpg
| image2_caption = Restoration of ''D. hesperus''
| taxon = Desmostylus
| authority = {{Harvnb|Marsh|1888}}
| subdivision_ranks = Species
| subdivision =
*†''D. hesperus'' ([type](/source/Type_species))
{{Harvnb|Marsh|1888}}
*†''D. coalingensis''
{{Harvnb|Reinhart|1959}}
*†''D. japonicus''
{{Harvnb|Tokunaga|Iwasaki|1914}}
| synonyms =
*†''Vanderhoofius coalingensis''
}}
'''''Desmostylus'''''["bound pillar", from [Greek](/source/Greek_language) {{lang|grc| δεσμός}} (''desmos''), bond, and {{lang|grc|στῦλος}} (''stulos''), pillar, referring to the shape of the molars.] is an [extinct](/source/extinction) genus of [herbivorous](/source/herbivorous) [mammal](/source/mammal) of the [family](/source/Family_(taxonomy)) [Desmostylidae](/source/Desmostylidae) living from the [Chattian](/source/Chattian) stage of the [Late Oligocene](/source/Late_Oligocene) subepoch through the [Late Miocene](/source/Late_Miocene) subepoch (28.4 [mya](/source/Annum)–7.250 Mya) and in existence for approximately {{Mya|28.4-7.2|million years}}.[{{Paleodb|36958|Desmostylus}}. Retrieved March 2013.]
==Description==
[[File:Desmostylus Skull.jpg|thumb|left|Skull of ''D. japonicus'' at the [National Museum of Nature and Science](/source/National_Museum_of_Nature_and_Science), [Tokyo](/source/Tokyo), [Japan](/source/Japan). [Holotype](/source/Holotype)]]
''Desmostylus'' was a large, [hippopotamus](/source/hippopotamus)-like creature, with the adult Keton specimen of ''D. hesperus'' measuring {{cvt|275|cm|ft}} in length, {{cvt|105|cm|ft}} in height and {{convert|1283|kg|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 {{convert|2.8|MT|ST}}.[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] It had a short tail and powerful legs with four [hooves](/source/claw). The animal's jaws were elongated and sported forward-facing [tusks](/source/tusks), which were elongated [canines](/source/canine_tooth) and [incisor](/source/incisor)s.[{{Harvnb|Palmer|1999| p=228}}]
Most likely fully aquatic, ''Desmostylus'' is thought to have lived in shallow water in coastal regions, usually less than 30 meters deep.[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.] Recent isotope work indicates that ''Desmostylus'' more likely lived (or spent a large amount of time) in freshwater or [estuary](/source/estuary) ecosystems foraging for aquatic freshwater plants.[{{Harvnb|Clementz|Hoppe|Koch|2003}}]
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.[{{cite journal|last1= Hayashi|first1= S.|last2= Houssaye|first2= A.|last3= Nakajima|first3= Y.|last4= Chiba|first4= K.|last5= Ando|first5= T.|last6= Sawamura|first6= H.|last7= Inuzuka|first7= N.|last8= Kaneko|first8= N.|last9= Osaki|first9= T.|title= Bone Inner Structure Suggests Increasing Aquatic Adaptations in Desmostylia (Mammalia, Afrotheria)|journal= PLOS ONE|volume= 8|issue= 4|year= 2013|article-number= e59146|doi= 10.1371/journal.pone.0059146|oclc= 837402105 |pmid= 23565143|pmc= 3615000|bibcode= 2013PLoSO...859146H|doi-access= free}}]
==Species==
''Desmostylus hesperus'' (synonyms and invalid names: ''D. watasei'', ''D. cymatias'', ''D. californicus'', ''D. mirabilis'', ''D. minor'', ''Desmostylella typica''),[{{Harvnb|Tomida|Ohta|2007|p=60}}][{{Harvnb|Inuzuka|Domning|Ray|1984}}] and ''D. japonicus''.
{{Harvnb|Marsh|1888}} named the type specimen ''D. hesperus'' based on a set of isolated teeth that had been found near [Mission San Jose, California](/source/Mission_San_Jose%2C_Fremont%2C_California) (type locality: {{Coord|37.6|-121.9|display=inline}}, paleocoordinates {{Coord|36.8|-117.6|display=inline}}).[{{Cite web
| title = Mission San Jose, east (Miocene of the United States) | publisher = Fossilworks
| url = https://paleobiodb.org/classic/displayCollResults?collection_no=13093 | access-date = 17 December 2021}}] Marsh described his specimen as a [sirenia](/source/sirenia)n and proposed affinities with ''[Metaxytherium](/source/Metaxytherium)'' (a genus of extinct dugongs) and ''Halicore'' (an obsolete name for dugong).[{{Harvnb|Marsh|1888|p=96}}]
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.[{{Harvnb|Uno|Kimura|2004|p=1}}]
''Desmostylus japonicus'' was described by {{Harvnb|Yoshiwara|Iwasaki|1902}} based on a well-preserved partial skull and named by {{Harvnb|Tokunaga|Iwasaki|1914}}. It has been reproposed as distinct species based on cranial morphology.