''Enaliarctos''From

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

, ''enalios'', of the sea; and , ''arktos'', bear, "referring to the arctoid, including ursid, Carnivora" (Mitchell & Tedford, 1973, p. 218). is 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 ...

of pinnipedimorph, and may represent the ancestor to all pinnipeds. The five species in the genus ''Enaliarctos'' have been recovered from late

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 ...

and early

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 ...

(ca. 28-17 million years ago) strata of

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

and

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

Description

It had a short

tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...

and developed limbs with webbed feet. Unlike modern

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, it had a set of slicing

carnassials 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 f ...

; the presence of slicing teeth (rather than purely piercing teeth as 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 Whiskers, also known as vibrissae (; vibrissa; ) are a type of stiff, functional hair used by most therian mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser as ta ...

, and a specialized

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

for hearing underwater.

Evolution

''Enaliarctos'' has been heralded as the ancestor of all known pinnipeds, including the families Otariidae (fur seals and sea lions),

Desmatophocidae Desmatophocidae is an extinct family of pinnipeds closely related to either the eared seals and walruses or to the earless seals. These animals were the first group of large-bodied pinnipeds to evolve, first appearing in the Early Miocene, with n ...

(extinct seal convergent pinnipeds), Phocidae (true seals), and

Odobenidae Odobenidae is a family of pinnipeds, of which the only extant species is the walrus (''Odobenus rosmarus''). In the past, however, the group was much more diverse, and includes more than a dozen fossil genera. Taxonomy All genera, except '' Od ...

(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, while 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, such as the more recently discovered '' Puijila'', of controversial affinities, though).''Enaliarctos emlongi'' is represented by

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

from coastal

. It existed between 13 and 20 million years ago, during the

Hemingfordian The Hemingfordian on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 20,600,000 to 16,300,000 years BP. It is usually considered to overlap the lates ...

age of the

epoch. It was named for renowned fossil collector Douglas Emlong in 1991 by paleontologist Annalisa Berta.

Notes

References

* Berta, A., C.E. Ray and A.R. Wyss. 1989. Skeleton of the oldest known pinniped, Enaliarctos mealsi. Science 244:60-62. *Berta, A. 1991. New ''Enaliarctos''* (Pinnipedimorpha) from the Miocene of Oregon and the role of "Enaliarctids" in Pinniped Phylogeny. Smithsonian Contributions to Paleobiology 69. * Dixon, D., Moody, R., Jenkins, I. and Zhuravlev, A.Y., ''Cassell's Atlas of Evolution''. Oxford 2001 * Mitchell, E., & Tedford, R.H. 1973. The Enaliarctinae: A new group of extinct aquatic Carnivora and a consideration of the origin of the Otariidae. ''Bulletin of the American Museum of Natural History'', 151(3), 203-284
available online
* Wallace, D.R. 2007. Neptune's Ark: From Ichthyosaurs to Orcas. University of California Press.

External links

''Enaliarctos'' at The Paleobiology Database
{{Taxonbar, from=Q747851 Oligocene pinnipeds Miocene pinnipeds Chattian genus first appearances Aquitanian genus extinctions Transitional fossils Prehistoric pinnipeds of North America Prehistoric carnivoran genera Fossil taxa described in 1973