''Potamotherium'' ('river beast') an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

caniform Caniformia is a suborder within the order Carnivora consisting of "dog-like" carnivorans. They include dogs (wolves, foxes, etc.), bears, raccoons, and mustelids. The Pinnipedia ( seals, walruses and sea lions) are also assigned to this gr ...

carnivoran Carnivora ( ) is an order of placental mammals specialized primarily in eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the sixth largest order of mammals, comprising at least 279 species. Carnivor ...

from the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

epoch of France and Germany. It has historically been assigned to the family

Mustelidae The Mustelidae (; from Latin , weasel) are a diverse family of carnivora, carnivoran mammals, including weasels, badgers, otters, polecats, martens, grisons, and wolverines. Otherwise known as mustelids (), they form the largest family in the s ...

(otters, weasels, etc.), but more recent studies suggest that it represents a primitive relative of

pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant taxon, extant families Odobenidae (whose onl ...

s (seals, sea lions, etc.)

Classification

The genus was first described in 1833. Carroll (1988) assigned it to the family

as a member of the subfamily Oligobuninae. However, it was recently suggested that ''Potamotherium'' was not a mustelid at all, but rather a very basal

. Berta et al. (2018) placed ''Potamotherium'' along with '' Puijila'' and '' Semantor'' in the family Semantoridae. Two species have been identified in the genus: ''P. valletoni'', the type species, and ''P. miocenicum''.

Distribution

Finds range from the mid-latitudes of

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, dated from the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

boundary and surviving through to the end of the Miocene. It has been interpreted by several researchers as a basal, non-marine ancestor of seals and

sea lion Sea lions are pinnipeds characterized by external ear flaps, long foreflippers, the ability to walk on all fours, short and thick hair, and a big chest and belly. Together with the fur seals, they make up the family Otariidae, eared seals. ...

s, suggesting a freshwater phase in the evolutionary transition of pinnipeds from land to sea; geochemical analysis supports this hypothesis, finding ''P. valletoni'' to have been a freshwater dweller. If ''Potamotherium'' was indeed a pinniped instead of a mustelid, its relatives were possibly early

bear Bears are carnivoran mammals of the family (biology), family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats ...

s (whose ancestors at the time were small and generally weasel-like).

Palaeobiology

Physically, ''Potamotherium'' resembled a modern

otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine. Lutrinae is a branch of the Mustelidae family, which includes weasels, badgers, mink, and wolverines, among ...

, and was long, with an elongated, slender body and short legs. With a flexible backbone and a streamlined shape, it was probably a good swimmer. Analysis of fossils suggests that ''Potamotherium'' had a poor sense of smell, but made up for this with good

vision Vision, Visions, or The Vision may refer to: Perception Optical perception * Visual perception, the sense of sight * Visual system, the physical mechanism of eyesight * Computer vision, a field dealing with how computers can be made to gain und ...

and

hearing Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory sci ...

. Fossils of ''Potamotherium'' are so complete that the shape of the brain can be inferred via a digital endocast of the skull. The coronal gyrus (a fold on the lateral surface of the brain) is broad, slanted backwards and partially split by a small groove. The brain is nearly identical to that of '' Enaliarctos'', an extinct mammal universally agreed to be close to pinnipeds. Modern pinnipeds and the extinct '' Pinnarctidion'' have an expanded coronal gyrus with a distinctive vertical orientation. The carnivorans with the largest coronal gyrus are freshwater foragers such as the otter civet (''Cynogale bennetti'') and certain otter species (in the genera ''

Lutra ''Lutra'' is a genus of otters, one of seven in the subfamily Lutrinae. Taxonomy and evolution The genus includes these species: Extant species Extinct species *†'' Lutra affinis'' *†'' Lutra bressana '' *†'' Lutra bravardi'' ...

'' and ''

Lontra ''Lontra'' is a genus of otters from the Americas. Species These species were previously included in the genus ''Lutra'', together with the Eurasian otter The Eurasian otter (''Lutra lutra''), also known as the European otter, Eurasian river ...

''). They primarily emphasize sensitive whiskers (vibrissae) or the lips while hunting, rather than the hands. It is likely that the same was true for ''Potamotherium''. Modern pinnipeds are unique among marine mammals for their large whiskers, which were probably inherited from an ancestor similar to ''Potamotherium''.

References

{{Taxonbar, from=Q1636008 Miocene pinnipeds Miocene mammals of North America Aquitanian genus first appearances Tortonian extinctions Prehistoric pinnipeds of North America Miocene mammals of Europe Fossil taxa described in 1833 Prehistoric carnivoran genera