Desmostylus is a monotypic

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 extinct genus of herbivorous mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 of the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

  Desmostylidae

Desmostylidae

Desmostylidae is an extinct family of herbivorous marine mammal belonging to the order of Desmostylia living along the coast of the Pacific Ocean from the Rupelian stage of the Early Oligocene through the Chattian stage of the Late Oligocene existing for approximately .Desmostylidae are...

living from the Chattian

Chattian

The Chattian is, in the geologic timescale, the youngest of two ages or upper of two stages of the Oligocene epoch/series. It spans the time between and . The Chattian is preceded by the Rupelian and is followed by the Aquitanian .-Stratigraphic definition:The Chattian was introduced by Austrian...

 stage of the Late Oligocene subepoch through the Late Miocene

Late Miocene

The Late Miocene is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch....

 subepoch (28.4 mya—7.250 Mya) and in existence for approximately .

Morphology

Desmostylus was a large, hippopotamus

Hippopotamus

The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...

-like creature of about 1.8 metres (5.9 ft) long which weighed about 200 kilograms (440.9 lb). It had a short tail and powerful legs with four hooves

Claw

A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...

. Both the creature's jaws were elongated and sported forward-facing tusks, which were elongated canines

Canine tooth

In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

 and incisor

Incisor

Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...

s.

Most likely amphibious

Amphibious

Amphibious means able to use either land or water. In particular it may refer to:*Amphibious warfare, warfare carried out on both land and water*Amphibians, vertebrate animals of the Class Amphibia...

, Desmostylus is thought to have lived in shallow water in coastal regions. Some paleontologists

Paleontology

Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...

have argued it may have fed on seaweed

Seaweed

Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...

 during low tide. However, recent isotope work indicates that Demostylus more likely lived in freshwater or estuary

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 ecosystems and ate aquatic freshwater plants.

Species

D. hesperus (syn. D. japonicus, D. watasei, D. cymatias, D. californicus, D. mirabilis, D. minor, Desmostylella typica)

Sister genera

Behemotops

Behemotops

Behemotops is an extinct genus of herbivorous marine mammal of the family Desmostylidae living from the Rupelian stage of the Early Oligocene subepoch through the Late Oligocene subepoch and in existence for approximately ....

, Cornwallius

Cornwallius

Cornwallius is an extinct herbivorous marine mammal of the family Desmostylidae. Cornwallius lived along the North American Pacific Coast from the Chattian stage of the Early Oligocene through the Oligocene and existing for approximately .-Fossil dfistribution:Like Desmostylus, fossils have been...

, Kronokotherium

Kronokotherium

Kronokotherium is an extinct herbivorous marine mammal of the genus Desmostylia of the family Desmostylidae. Kronokotherium lived along the North American Pacific Coast from the Chattian stage of the Late Oligocene through the Aquitanian stage of the Early Miocene and existing for approximately...

, Paleoparadoxia

Paleoparadoxia

Paleoparadoxia is a genus of large, herbivorous marine mammals that inhabited the northern Pacific coastal region during the Miocene epoch . It ranged from the waters of Japan , to Alaska to the north, and down to Baja California, Mexico...

, Vanderhoofius

Vanderhoofius

Vanderhoofius is an extinct genus of herbivorous marine mammal of the family Desmostylidae living from the Middle Miocene subepoch and in existence for approximately .-Morphology:...

Fossil distribution

Fossils have been discovered from along the northern Pacific Rim

Pacific Rim

The Pacific Rim refers to places around the edge of the Pacific Ocean. The term "Pacific Basin" includes the Pacific Rim and islands in the Pacific Ocean...

 from Baja, Mexico northward along the coast of California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

, Washington and west to Sakhalin Island, Hokkaido, Japan, and south to the Shimane Prefecture

Shimane Prefecture

is a prefecture of Japan located in the Chūgoku region on Honshū island. The capital is Matsue. It is the second least populous prefecture in Japan, after its eastern neighbor Tottori. The prefecture has an area elongated from east to west facing the Chūgoku Mountain Range on the south side and to...

, Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.