Enaliarctos Temporal range: Late Oligocene - Early Miocene, 28–17 Ma PreꞒ Ꞓ O S D C P T J K Pg N [1]
Enaliarctos mealsi cast of a specimen from California. At the AMNH.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Clade:	Pinnipedimorpha
Family:	†Enaliarctidae Mitchell & Tedford, 1973
Genus:	†Enaliarctos Mitchell & Tedford, 1973
Species
E. mealsi (type) E. barnesi E. emlongi E. mitchelli E. tedfordi

Enaliarctos^[2] is an extinct genus of pinnipedimorph, and may represent the ancestor to all pinnipeds. The five species in the genus Enaliarctos have been recovered from late Oligocene and early Miocene (ca. 28-17 million years ago) strata of California and Oregon.^[1]

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 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, and a specialized inner ear for hearing 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, 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 from coastal Oregon. It existed between 13 and 20 million years ago, during the Hemingfordian age of the Miocene epoch. It was named for renowned fossil collector Douglas Emlong in 1991 by paleontologist Annalisa Berta.

• Enaliarctos at The Paleobiology Database

v t e Genera of pinnipeds and their stem-allies
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Suborder: Caniformia Infraorder: Arctoidea
Pan-Pinnipedia †Amphicynodontidae Allocyon Amphicticeps Amphicynodon Drassonax Kolponomos Pachycynodon Parictis Wangictis †Semantoridae Necromites Potamotherium Puijila Semantor Pinnipedimorpha †Enaliarctos Pinnipediformes †Pacificotaria †Pinnarctidion †Pteronarctos Pinnipedia Phocidae †Devinophoca Monachinae †Magnotherium Monachini †Afrophoca †Auroraphoca †Messiphoca Monachus Neomonachus †Eomonachus †Noriphoca †Palmidophoca †Pliophoca †Pontophoca †Pristiphoca †Terranectes Miroungini †Callophoca Mirounga Lobodontini †Acrophoca †Australophoca †Hadrokirus †Homiphoca Hydrurga Leptonychotes Lobodon Ommatophoca †Piscophoca †Properiptychus †Virginiaphoca Phocinae †Cryptophoca †Frisiphoca †Kawas †Leptophoca †Monachopsis †Monotherium †Phocanella †Prophoca †Sarmatonectes Erignathini Erignathus †Platyphoca Cystophorini Cystophora †Miophoca †Pachyphoca Phocini †Batavipusa †Gryphoca Halichoerus Histriophoca †Nanophoca Pagophilus Phoca †Planopusa †Praepusa Pusa Otarioidea see below↓
Otarioidea †Desmatophocidae Allodesmus Atopotarus Desmatophoca Eodesmus Odobenidae †Archaeodobenus †Imagotaria †Kamtschatarctos †Nanodobenus †Neotherium †Osodobenus †Pelagiarctos †Pontolis †Proneotherium †Prototaria †Pseudotaria †Titanotaria Neodobenia †Dusignathinae Dusignathus Gomphotaria Odobeninae †Aivukus Odobenus †Ontocetus †Pliopedia †Protodobenus †Valenictus Panotariidae †Eotaria Otariidae Callorhinae Callorhinus †Pithanotaria Otariinae †Thalassoleon Zalophini Eumetopias †Oriensarctos †Proterozetes Zalophus Otariini Arctocephalus Arctophoca †Hydrarctos Neophoca Otaria Phocarctos
Lists List of pinnipeds List of fossil pinnipedimorphs