Desmostylidae is an extinct

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their reli ...

s belonging to the order of

Desmostylia The Desmostylia (from Greek δεσμά ''desma'', "bundle", and στῦλος ''stylos'', "pillar") are an extinct order of aquatic mammals that existed from the early Oligocene (Rupelian) to the late Miocene (Tortonian) (). Desmostylians are t ...

. They lived in the coastal waters of the northern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

from the

Early Oligocene The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chatti ...

(

Rupelian The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chattian ...

) through the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

(

Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Torton ...

) (33.9 mya—7.2 MYA) . Retrieved April 2020.K. Chiba, A. R. Fiorillo, L. L. Jacobs, Y. Kimura, Y. Kobayashi, N. Kohno, Y. Nishida, M. J. Polcyn, and K. Tanaka. 2016. A new desmostylian mammal from Unalaska (USA) and the robust Sanjussen jaw from Hokkaido (Japan), with comments on feeding in derived desmostylids. Historical Biology 28(1-2):289-303 existing for approximately .

Taxonomy and systematics

Desmostylidae was named by . It was assigned to

Sirenia The Sirenia (), commonly referred to as sea-cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The Sirenia currently comprise two distinct f ...

by Osborn (1905); to

Proboscidea The Proboscidea (; , ) are a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. From ...

by Abel (1919); to Desmostyliformes by Simpson (1932), Kretzoi (1941) and Reinhart (1959); to

by McKenna and Bell (1997); and to Desmostylia by Carroll (1988), Inuzuka et al. (1995), Inuzuka (2000) and Barnes and Goedert (2001). found a subadult specimen of ''

Behemotops ''Behemotops'' (from the Biblical monster Behemoth, by Linnaeus and others believed to be a hippo) is an extinct genus of herbivorous marine mammal. It lived from the Early Oligocene (Rupelian) through the Late Oligocene (33.9 mya—23 Mya), e ...

proteus'' on

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...

in 2007. They noted that (1) the cranial features of their specimen were similar to those of ''

Cornwallius ''Cornwallius'' is an extinct herbivorous marine mammal of the family Desmostylidae. ''Cornwallius'' lived along the North American Pacific Coast from the Early Oligocene ( Chattian) through the Oligocene (28.4 mya—20.6 Mya) and existing for ...

'' and that (2) the

adult dentition Permanent teeth or adult teeth are the second set of tooth, teeth formed in diphyodont mammals. In humans and old world simians, there are thirty-two permanent teeth, consisting of six maxillary and six human mandible, mandibular molar (tooth), mo ...

was not delayed in their specimen, unlike in ''

Desmostylus ''Desmostylus'' is an extinct genus of herbivorous mammal of the family Desmostylidae living from the Chattian stage of the Late Oligocene subepoch through the Late Miocene subepoch (28.4 mya—7.250 Mya) and in existence for approximately . ...

'' and other

Afrotheria Afrotheria ( from Latin ''Afro-'' "of Africa" + ''theria'' "wild beast") is a clade of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews (also know ...

, and they concluded that (1) Desmostylidae and Paleoparadoxiidae probably diverged earlier than previously believed and that (2) delayed dentition can not be the most primitive state of Desmostylia.

Classification

Classification after Chib 2016: * Desmostylidae: ** ''

'' ** ''

Kronokotherium ''Kronokotherium'' is an extinct herbivorous marine mammal of the family Desmostylidae in the order Desmostylia. Its type locality is Raktinskaya, Kamchatka Peninsula, Russia (, paleocoordinates ). ''Kronokotherium'' was made a separate genus ...

'' ** '' Ounalashkastylus''

References

* * * Desmostylians Oligocene mammals Miocene mammals Tortonian extinctions Rupelian first appearances Prehistoric mammal families {{Paleo-mammal-stub