Acrophoca

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Acrophoca
Temporal range: Late Miocene
~7.246–5.332  Ma
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Acrophoca skeleton at the National Museum of Natural History in Washington, D.C.jpg
Display at the Smithsonian National Museum of Natural History
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Clade: Pinnipedia
Family: Phocidae
Subfamily: Monachinae
Tribe: Lobodontini
Genus: Acrophoca
Muizon, 1981
Species:
A. longirostris
Binomial name
Acrophoca longirostris
Muizon, 1981

Acrophoca longirostris, sometimes called the swan-necked seal, is an extinct genus of Late Miocene pinniped. It was thought to have been the ancestor of the modern leopard seal; however, it is now thought to be a species of monk seal.

Contents

Taxonomy

Fossil in Peru Acrophoca.jpg
Fossil in Peru

The fossils of A. longirostris have been discovered in the Pisco Formation of Peru and the Bahía Inglesa Formation of Chile. [1] When it was first described in 1981, it was thought to have been closely related to the lobodontine seals which includes the modern day leopard seal (Hydrurga leptonyx), the crabeater seal (Lobodon carcinophaga), the Weddell seal (Leptonychotes weddelli), and the Ross seal (Ommatophoca rossii). However, it is now thought to be a basal species of monk seal of the subfamily Monachinae, closely related to the extinct seal Piscophoca . [2] [3]

Description

Restoration Acrophoca BW.jpg
Restoration

Acrophoca was around 1.5 metres (5 ft) long, and was not as well-adapted to swimming as its descendants, possessing less developed flippers and a less streamlined neck. This may indicate that it spent a lot of time near the coast. Its teeth were built for piercing, implying a diet consisted primarily of fish. However, it also had interdigitated tooth cusps causing the teeth on the upper jaw to fit with the teeth of the lower jaw, which is consistent with filter feeders. Unlike other earless seals, Acrophoca had a long and flexible neck, with an elongated body. The orientation of the pelvis, which in comparison to modern earless seals is everted, as well as adaptations to the hind limbs suggest that swimming was mainly powered by the back flippers. It was less adapted for the sea than the lobodontine seals, suggesting it inhabited nearshore waters. [3] [4]

Paleoecology

Its fossils have been found alongside those of the marine sloth Thalassocnus and tusked cetacean Odobenocetops , as well as modern animals such as bottlenose dolphins, gannets and cormorants.

Related Research Articles

<span class="mw-page-title-main">Carnivora</span> Order of mammals

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 on every major landmass and in a variety of habitats, ranging from the cold Polar regions of Earth the hyper-arid region of the Sahara Desert to the open seas. They have a very large array of different body plans with a wide diversity of shapes and sizes.

<span class="mw-page-title-main">Earless seal</span> Family of mammals

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.

<span class="mw-page-title-main">Eared seal</span> Family of marine mammals

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.

<span class="mw-page-title-main">Pinniped</span> Taxonomic group of semi-aquatic mammals

Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, 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 group. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.

<span class="mw-page-title-main">Leopard seal</span> Macropredatory species of Antarctic seal

The leopard seal, also referred to as the sea leopard, is the second largest species of seal in the Antarctic. Its only natural predator is the orca. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".

<span class="mw-page-title-main">Monk seal</span> Tribe of earless seals

Monk seals are earless seals of the tribe Monachini. They are the only earless seals found in tropical climates. The two genera of monk seals, Monachus and Neomonachus, comprise three species: the Mediterranean monk seal, Monachus monachus; the Hawaiian monk seal, Neomonachus schauinslandi; and the Caribbean monk seal, Neomonachus tropicalis, which became extinct in the 20th century. The two surviving species are now rare and in imminent danger of extinction. All three monk seal species were classified in genus Monachus until 2014, when the Caribbean and Hawaiian species were placed into a new genus, Neomonachus.

<span class="mw-page-title-main">Flipper (anatomy)</span> Flattened limb adapted for propulsion and maneuvering in water

A flipper is a broad, flattened limb adapted for aquatic locomotion. It refers to the fully webbed, swimming appendages of aquatic vertebrates that are not fish.

<span class="mw-page-title-main">Caniformia</span> Suborder of mammals

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.

<span class="mw-page-title-main">Carnassial</span> Mammal tooth type

Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified fourth upper premolar and the first lower molar. These teeth are also referred to as sectorial teeth.

Potamotherium an extinct genus of caniform carnivoran from the Miocene epoch of France and Germany. It has historically been assigned to the family Mustelidae, but more recent studies suggest that it represents a primitive relative of pinnipeds

<i>Imagotaria</i> Extinct genus of carnivores

Imagotaria is an extinct monotypic genus of walrus with the sole species Imagotaria downsi. Fossils of Imagotaria are known from the early late Miocene of California.

<i>Prorastomus</i> Extinct genus of mammals

Prorastomus sirenoides is an extinct species of primitive sirenian that lived during the Eocene Epoch 40 million years ago in Jamaica.

<i>Rytiodus</i> Extinct genus of sirenian

Rytiodus is an extinct genus of sirenian, whose fossils have been discovered in France, Europe and Libya.

<i>Prosqualodon</i> Extinct genus of mammals

Prosqualodon is an extinct genus of Early to Middle Miocene cetacean from Argentina, Australia, New Zealand and Venezuela.

<i>Eurhinodelphis</i> Extinct genus of mammals

Eurhinodelphis is an extinct genus of Miocene cetacean. Its fossils have been found in Belgium, France, and Maryland.

<i>Sivatherium</i> Extinct genus of mammals

Sivatherium is an extinct genus of giraffid that ranged throughout Africa and Eurasia. The species Sivatherium giganteum is, by weight, one of the largest giraffids known, and also one of the largest ruminants of all time.

<i>Propliopithecus</i> Extinct genus of primates

Propliopithecus is an extinct genus of primate.

<i>Puijila</i> Extinct genus of primitive pinnipeds

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.

<span class="mw-page-title-main">Monachinae</span> Subfamily of carnivores

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.

<i>Atopotarus</i> Extinct genus of carnivorans

Atopotarus is an extinct genus of pinniped from the middle Miocene known from one specimen from Los Angeles County, California. It belongs to the extinct family Desmatophocidae, an early lineage of seal-like pinnipeds from the North Pacific.

References

  1. "Acrophoca". Fossilworks . Gateway to the Paleobiology Database . Retrieved 23 November 2017.
  2. Alva, J. J. (2017). Tropical Pinnipeds: Bio-Ecology, Threats and Conservation. CRC Press. p. 27. ISBN   978-1-351-64763-2.
  3. 1 2 Berta, A. (2012). Return to the Sea: The Life and Evolutionary Times of Marine Mammals. University of California Press. pp. 58–59. ISBN   978-0-520-27057-2.
  4. Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 226. ISBN   1-84028-152-9.

Further reading