Enaliarctos

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Enaliarctos

Enaliarctos is an extinct genus of pinniped

Pinniped

Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae ....
.

Five species in the genus Enaliarctos represent the oldest known pinniped fossils, and have been recovered from the late Oligocene
Oligocene

The Oligocene is a geologic epoch of the Paleogene Geologic Timescale and extends from about 33.9 million to 23 million years before the present....
and early Miocene
Miocene

The Miocene is a Geologic time scale of the Neogene period and extends from about 23.03 to 5.33 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified but the exact dates of the start and end of the period are uncertain....
(ca. 24-22 million years ago) of California
California

California is a U.S. state on the West Coast of the United States of the United States, along the Pacific Ocean. It is bordered by Oregon to the north, Nevada to the east, Arizona to the southeast, and to the south the Mexico state of Baja California....
and Oregon
Oregon

Oregon is a U.S. state in the Pacific Northwest region of the United States. The area was inhabited by many indigenous tribes before the arrival of traders, explorers and settlers....
. It had a short tail
Tail

The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals and birds....
and developed limbs with webbed feet. Unlike modern sea lions, it had a set of slicing carnassials; the presence of slicing (rather than purely piercing teeth in modern fish eating pinnipeds) suggests that Enaliarctos needed to return to shore with prey items in order to masticate and ingest them.

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Encyclopedia

Enaliarctos is an extinct genus of pinniped
Pinniped

Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semi-aquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae ....
.

Five species in the genus Enaliarctos represent the oldest known pinniped fossils, and have been recovered from the late Oligocene
Oligocene

The Oligocene is a geologic epoch of the Paleogene Geologic Timescale and extends from about 33.9 million to 23 million years before the present....
and early Miocene
Miocene

The Miocene is a Geologic time scale of the Neogene period and extends from about 23.03 to 5.33 million years before the present. As with other older geologic periods, the rock beds that define the start and end are well identified but the exact dates of the start and end of the period are uncertain....
(ca. 24-22 million years ago) of California
California

California is a U.S. state on the West Coast of the United States of the United States, along the Pacific Ocean. It is bordered by Oregon to the north, Nevada to the east, Arizona to the southeast, and to the south the Mexico state of Baja California....
and Oregon
Oregon

Oregon is a U.S. state in the Pacific Northwest region of the United States. The area was inhabited by many indigenous tribes before the arrival of traders, explorers and settlers....
. It had a short tail
Tail

The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals and birds....
and developed limbs with webbed feet. Unlike modern sea lions, it had a set of slicing carnassials; the presence of slicing (rather than purely piercing teeth in modern fish eating pinnipeds) suggests that Enaliarctos needed to return to shore with prey items in order to masticate and ingest them. Still, Enaliarctos had some sea lion-like characteristics such as large eyes, sensitive whiskers
Vibrissae

Vibrissae , or whiskers, are specialized hairs, usually employed for tactile sensation, but can also refer to the stiff feathers near the mouths of some birds....
and a specialized inner ear
Inner ear

The inner ear is the labyrinth , a system of passages comprising two main functional parts:* the organ of hearing, or cochlea* and the vestibular apparatus, the organ of balance that consists of three semicircular canals and the Vestibule of the ear....
for hearing sound underwater.

Enaliarctos has been heralded as the ancestor of all known pinnipeds, including the families Otariidae (fur seals and sea lions), Desmatophocidae (extinct seal convergent pinnipeds), Phocidae (true seals), and Odobenidae (walruses). Investigations of the biomechanics of Enaliarctos indicate that it used both its forelimbs and hindlimbs during swimming. Modern fur seals and sea lions only use their forelimbs, while true seals primarily use their hindlimbs for aquatic propulsion; lastly, the extant walrus uses both fore- and hindlimbs for swimming. It has been postulated that the condition in Enaliarctos is ancestral for all pinnipeds, and that forelimb swimming was lost in true seals, and hindlimb swimming was lost in fur seals and sea lions. This is significant because there has been considerable debate as to whether pinnipeds share common ancestry. Interpretation of Enaliarctos indicates that all pinnipeds share a common ancestor (which, if it was not Enaliarctos, must have been something very similar).
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