Skeletal morphology and locomotor capabilities of the archaic pinnipedEnaliarctos mealsi

A virtually complete skeleton of the pinniped Enaliarctos mealsi is described from the Pyramid Hill Sandstone Member of the Jewett Sand (late Oligocene or early Miocene) in central California. Skeletal evidence supports the sister group relationship of ursids and pinnipeds and the monophyly of pinnipeds. The structure of the vertebral column, especially the long transverse processes on the lumbar vertebrae and loose-fitting zygapophyses, indicates that the spine was capable of considerable flexion and extension. The limbs, modified as flippers with strongly developed bony processes and expanded areas for muscle attachment, provide evidence of their use in both aquatic and terrestrial locomotion.