Potamotherium Temporal range: Aquitanian - Tortonian | |
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P. valletoni skeleton | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Family: | † Semantoridae |
Genus: | † Potamotherium Geoffroy, 1833 |
Species | |
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Potamotherium ('river beast') an extinct genus of caniform carnivoran from the Miocene epoch of France and Germany. It has historically been assigned to the family Mustelidae (otters, weasels, etc.), but more recent studies suggest that it represents a primitive relative of pinnipeds (seals, sea lions, etc.)
The genus was first described in 1833. Carroll (1988) assigned it to the family Mustelidae 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 pinniped. [1] [2] Berta et al. (2018) placed Potamotherium along with Puijila and Semantor in the family Semantoridae. [3]
Two species have been identified in the genus: P. valletoni, the type species, and P. miocenicum. [4]
Finds range from the mid-latitudes of Europe and North America, dated from the Oligocene/Miocene boundary and surviving through to the end of the Miocene. [5] [6] It has been interpreted by several researchers as a basal, non-marine ancestor of seals and sea lions, suggesting a freshwater phase in the evolutionary transition of pinnipeds from land to sea. If Potamotherium was indeed a pinniped instead of a mustelid, its relatives were possibly early bears (whose ancestors at the time were small and generally weasel-like). [2]
Physically, Potamotherium resembled a modern otter, and was 1.5 metres (5 ft) 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 and hearing. [7]
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 and Lontra ). 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. [8]
Carnivora is an order of placental mammals that have specialized in primarily eating flesh, whose members are formally referred to as carnivorans. The order Carnivora is the fifth largest order of mammals, comprising at least 279 species.
The earless seals, phocids, or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae. They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.
The Mustelidae are a diverse family of carnivorous mammals, including weasels, badgers, otters, martens, and wolverines. Otherwise known as mustelids, they form the largest family in the suborder Caniformia of the order Carnivora with about 66 to 70 species in nine subfamilies.
An eared seal, otariid, or otary is any member of the marine mammal family Otariidae, one of three groupings of pinnipeds. They comprise 15 extant species in seven genera and are commonly known either as sea lions or fur seals, distinct from true seals (phocids) and the walrus (odobenids). Otariids are adapted to a semiaquatic lifestyle, feeding and migrating in the water, but breeding and resting on land or ice. They reside in subpolar, temperate, and equatorial waters throughout the Pacific and Southern Oceans, the southern Indian, and Atlantic Oceans. They are conspicuously absent in the north Atlantic.
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semi-aquatic, and mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic lineage. Pinnipeds belong to the clade Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.
Caniformia is a suborder within the order Carnivora consisting of "dog-like" carnivorans. They include dogs, bears, raccoons, and mustelids. The Pinnipedia are also assigned to this group. The center of diversification for the Caniformia is North America and northern Eurasia. Caniformia stands in contrast to the other suborder of Carnivora, the Feliformia, the center of diversification of which was in Africa and southern Asia.
Enaliarctos is an extinct genus of pinnipedimorph, and may represent the ancestor to all pinnipeds. Prior to the discovery of Puijila, the five species in the genus Enaliarctos represented the oldest known pinnipedimorph fossils, having been recovered from late Oligocene and early Miocene strata of California and Oregon.
Desmatophoca is an extinct genus of early pinniped that lived during the Miocene, and is named from the Greek "phoca", meaning seal. A taxon of the family Desmatophocidae, it shares some morphological similarities with modern true seals. Two species are recognized: Desmatophoca oregonensis and Desmatophoca brachycephala. Little information exists regarding Desmatophoca, due to the small number of fossil samples obtained and identified.
Ursoidea is a superfamily of arctoid carnivoran mammals that includes the families Subparictidae, Amphicynodontidae, and Ursidae which the last family includes the extant lineages of bears as well the extinct Hemicyoninae and Ursavinae. The interrelationships of ursoids has had slight arrangements. In the past it was thought the extinct Amphicyonidae were stem-bears based on morphological analysis of the ear region, though the most recent publications on early amphicyonids suggests they were basal caniforms. The amphicynodontids are sometimes classified as either a subfamily of bears, a paraphyletic assemblage of early bears, or even stem-pinnipeds. The subparictids were previously classified as amphicynodontine/ids. The hemicyonines have been occasionally reclassified as a separate family.
Kolponomos is an extinct genus of carnivoran mammal that existed in the Late Arikareean North American Land Mammal Age, early Miocene epoch, about 20 million years ago. It was likely a marine mammal. The genus was erected in 1960 by Ruben A. Stirton, a paleontologist at the University of California Museum of Paleontology, Berkeley, for the species K. clallamensis, on the basis of a partial skull and jaw found on the Olympic Peninsula. At the time, Stirton questionably assigned it to Procyonidae, its systematic position remained problematic until the discovery of more fossils including a nearly complete cranium from the original locality of K. clallamensis which helped identify it as part of the group from which pinnipeds evolved.
Musteloidea is a superfamily of carnivoran mammals united by shared characteristics of the skull and teeth. Musteloids are the sister group of pinnipeds, the group which includes seals.
Oligobuninae is an extinct subfamily of the family Mustelidae known from Miocene deposits in North America.
Puijila darwini is an extinct species of stem-pinniped which lived during the Miocene epoch about 21 to 24 million years ago. Approximately a metre in length, the animal possessed only minimal physical adaptations for swimming. Unlike modern pinnipeds, it did not have flippers and its overall form was otter-like, albeit more specialized; its skull and teeth are the features that most clearly indicate that it is a seal.
Arctoidea is a clade of mostly carnivorous mammals which include the extinct Hemicyonidae (dog-bears), and the extant Musteloidea, Pinnipedia, and Ursidae (bears), found in all continents from the Eocene, 46 million years ago, to the present. The oldest group of the clade is the bears, as their CMAH gene is still intact. The gene became non-functional in the common ancestor of the Mustelida. Arctoids are caniforms, along with dogs (canids) and extinct bear dogs (Amphicyonidae). The earliest caniforms were superficially similar to martens, which are tree-dwelling mustelids. Together with feliforms, caniforms compose the order Carnivora; sometimes Arctoidea can be considered a separate suborder from Caniformia and a sister taxon to Feliformia.
Enhydritherium terraenovae is an extinct marine otter endemic to North America that lived during the Miocene through Pliocene epochs from ~9.1–4.9 Ma. (AEO), existing for approximately 4.2 million years.
Amphicynodontidae is a probable clade of extinct arctoids. While some researchers consider this group to be an extinct subfamily of bears, a variety of morphological evidence links amphicynodontines with pinnipeds, as the group were semi-aquatic otter-like mammals. In addition to the support of the pinniped–amphicynodontine clade, other morphological and some molecular analyses support bears being the closest living relatives to pinnipeds. According to McKenna and Bell (1997) Amphicynodontinae are classified as stem-pinnipeds in the superfamily Phocoidea. Fossils of these mammals have been found in Europe, North America and Asia. Amphicynodontines should not be confused with Amphicyonids (bear-dogs), a separate family of Carnivora which is a sister clade to arctoids within the caniforms, but which may be listed as a clade of extinct arctoids in older publications.
Semantoridae is an extinct family of stem-pinnipeds with fossils found in France, Kazakhstan, and Canada, dating back to various points in time in the Miocene epoch. Based on their overall anatomy semantorids were not marine specialists, as their elongated bodies, a long tail and robust limbs suggest they were freshwater animals not unlike otters. Indeed, at least some taxa such as Semantor and Potamotherium were initially classified as mustelids closely related to otters.
Enhydrictis is a genus of extinct mustelid, belonging to the subfamily Galictinae. The type species, and best known, is Enhydrictis galictoides from the Pleistocene of Sardinia and Corsica. Some authors attribute species from mainland Eurasia to the genus, but this is disputed, with others considering the genus endemic to Sardinia-Corsica.
Subparictidae is an extinct family of early Paleogene arctoid carnivorans endemic to North America that closely related to bears. They were small, raccoon-like mammals that lived from the Eocene to the early Miocene. This family includes a handful of genera such as Subparictis, Parictis, Nothocyon, and Eoarctos.