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.
Odobenidae is a family of pinnipeds. The only living species is the walrus. In the past, however, the group was much more diverse, and includes more than a dozen fossil genera.
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals in the clade Pinnipedia. They comprise the extant families Odobenidae, Otariidae, and Phocidae. There are 34 extant species of pinnipeds, and more than 50 extinct species have been 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 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 pinniped, 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 pinniped fossils, having been recovered from late Oligocene and early Miocene strata of California and Oregon.
Douglas Ralph Emlong was an amateur fossil collector from the Oregon Coast in the northwestern United States. His collections contributed to the discovery and description of numerous extinct marine mammal species, many of which are ancestral to extant groups. Described as an 'indefatigable' fossil collector with 'Promethian prowess in discovery of unprecedented vertebrate fossils', he contributed substantially to the field from the age of fourteen. The ancestral pinniped Enaliarctos emlongi was named in his honor by Annalisa Berta in 1991.
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.
Aetiocetus is a genus of extinct basal mysticete, or baleen whale that lived 33.9 to 23.03 million years ago, in the Oligocene in the North Pacific ocean, around Japan, Mexico, and Oregon, U.S. It was first described by Douglas Emlong in 1966 and currently contains known four species, A. cotylalveus, A. polydentatus, A. tomitai, and A. weltoni. These whales are remarkable for their retention of teeth and presence of nutrient foramina, indicating that they possessed baleen. Thus, Aetiocetus represents the transition from teeth to baleen in Oligocene mysticetes. Baleen is a highly derived character, or synapomorphy, of mysticetes, and is a keratinous structure that grows from the palate, or roof of the mouth, of the whale. The presence of baleen is inferred from the fossil record in the skull of Aetiocetus. Aetiocetus is known from both sides of the Pacific Ocean: it was first documented in Oregon, United States, but it is also known from Japan and Mexico. The genus is currently constrained to the Northern hemisphere and has little value in biostratigraphic studies of the Oligocene due to its limited occurrences across the Pacific.
Phocinae is a subfamily of Phocidae whose distribution is found in the seas surrounding the Holarctic, with the Baikal seal being the world's only freshwater species of pinniped. What distinguishes them from other phocid seals is the presence of well-developed claws on their front and back flippers. The Phocinae is divided into three extant tribes: Erignathini, Cystophorini, and Phocini. Members of both Erignathini and Cystophorini have 34 chromosomes, while species in the tribe Phocini have 32 chromosomes.
Allodesmus is an extinct genus of pinniped from the middle to late Miocene of California and Japan that belongs to the extinct pinniped family Desmatophocidae.
Pelagiarctos was a genus of walrus that lived during the Mid Miocene, approx. 13-15 mya. Its remains have been found in the Sharktooth Hill Bonebed, in Kern County, California. It was originally described as an Otariidae, though it is now usually considered to be a basal Odobenidae.
Puijila darwini is an extinct species of basal 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.
Pontolis is a large extinct genus of walrus. It contained three species, P. magnus, P. barroni, and P. kohnoi.
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.
Prototaria is an extinct genus of pinniped that lived approximately 15.97 to 13.65 mya during the Middle Miocene in what is now Japan. It belonged to the family Odobenidae, the only extant species of which is the walrus. Members of the genus Prototaria are believed to be the most basal imagotariine pinnipeds.
Proneotherium is an extinct genus of pinniped that lived approximately 20.43 to 15.97 mya during the Early Miocene in what is now Oregon, U.S.A. It belonged to the family Odobenidae, the only extant species of which is the walrus.
Monachinae is a subfamily of Phocidae whose distribution is found in the tropical, temperate and polar regions of the southern hemisphere, though in the distant past fossil representatives have been found on both sides of the North Atlantic Ocean. The difference between members of this group and members of Phocinae is in monachines the hindclaws are greatly reduced in size. Furthermore, all species have 34 chromosomes. There are three tribes recognized here: Monachini, Miroungini, and Lobodontini. While today represented by eight extant and one recently extinct species, Monachinae had an incredibly enriched fossil diversity that went into decline soon to be replaced by southern species of sea lions and fur seals.
Osodobenus is an extinct genus of walrus from the Miocene to Pliocene of California. Osodobenus may have been the first tusked walrus and shows several adaptations that suggest it was a suction feeder, possibly even a benthic feeder like modern species. Three skulls are known showing pronounced sexual dimorphism, with the female lacking the same tusks as the male. Only a single species, Osodobenus eodon, is currently recognized.
