Enaliarctos

Taxobox
name = "Enaliarctos"
status = fossil


image_caption = "Enaliarctos emlongi" and "Macrodelphinus" (background).
fossil_range = Late Oligocene - Early Miocene
regnum = Animalia
phylum = Chordata
classis = Mammalia
ordo = Carnivora
infraordo = Pinnipeda
familia = Enaliarctidae
genus = "Enaliarctos"
genus_authority = Mitchell & Thedford, 1973
subdivision_ranks = Species
subdivision =
* "E. mealsi" (type)
* "E. barnesi"
* "E. emlongi"
* "E. mitchelli"
* "E. tedfordi"'

"Enaliarctos" is an extinct genus of pinniped.

Five species in the genus "Enaliarctos" represent the oldest known pinniped fossils, and have been recovered from the late Oligocene and early Miocene (ca. 24-22 million years ago) of California and Oregon. It had a short tail 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 and a specialized inner ear for hearing sound under water.

"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).

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

External links

[http://paleodb.org/cgi-bin/bridge.pl?action=checkTaxonInfo&taxon_no=36916&is_real_user=0 "Enaliarctos" at The Paleobiology Database]