Named By: Mitchell & Thedford - 1973.
Classification: Chordata, Mammalia, Carnivora, Pinnipeda, Enaliarctidae.
Species: E. mealsi (type), E. barnesi, E. emlongi, E. mitchelli, E. tedfordi.
Size: Around 1.5 meters long.
Known locations: USA, California and Oregon.
Time period: Chattian of the Oligocene to Early Miocene.
Fossil representation: Many specimens.
has been commonly included in books about prehistoric animals where it
is credited as being the first pinniped, the groups that seals, sea
lions and walruses all belong to. The 2009 description of Puijila
however has taken some of the limelight away since this is even more
primitive pinneped in form that more clearly shows the transition
between land living ancestors and more aquatic descendants. One often
overlooked fact however is that some remains of Enaliarctos
come from the late Oligocene period which means that they actually
predate the Puijila type specimen. Despite this Puijila
certainly does represent a more primitive form of pinneped than
Enaliarctos, but it does suggest that they
continued to survive in
their existing form despite the advancements made by other genera such
One key area of study concerning Enaliarctos is how it swam. Today sea lions and fur seals (those with external ears) swim with only their front limbs, while true seals (those with just ear holes rather than eternal ear lobes) swim with only the rear limbs. Enaliarctos however seems to have swum with both fore and hind limbs, an idea supported by biomechanical study. This indicates that as early pinnepeds evolved to be better suited to swimming they initially swam with all fore limbs until they specialised down one form of locomotion other the other.
Aside from locomotion another trait that reveals the primitive nature of Enaliarctos is the dentition. Modern pinnepeds have teeth for crunching and puncturing, but Enaliarctos also retained slicing teeth towards the back of the mouth. This has been taken as an indication that would have had to return to land to eat the animals that it caught at sea. Enaliarctos was well adapted for hunting under water as evidenced by spaces for large eyes, well developed whiskers and hearing that had developed to work well under the water.