Science. 1989 Apr 7;244(4900):60-2. doi: 10.1126/science.244.4900.60.
A nearly complete skeleton of the archaic pinniped Enaliarctos, found in late Oligocene or early Miocene rocks (approximately 23 million years old) of California, provides new evidence on the origin of pinnipeds. Enaliarctos retains many primitive features expected in the hypothesized common ancestor of pinnipeds. Skeletal modifications seen in Enaliarctos document swimming adaptations and indicate that pinnipeds primitively used the axial skeleton and both fore and hindflippers as sources of propulsion. Elongate hindlimbs with prominent bony processes (reflecting powerful musculature) suggest that Enaliarctos was more active on land than modern pinnipeds.
一具近乎完整的古鳍足类动物——恩氏古海豹的骨架，发现于加利福尼亚晚渐新世或早中新世的岩石中（距今约 2300 万年），为鳍足类动物的起源提供了新证据。恩氏古海豹保留了许多在假设的鳍足类动物共同祖先中预期的原始特征。在恩氏古海豹中观察到的骨骼变化证明了其适应游泳的能力，并表明鳍足类动物最初使用轴骨骼和前肢和后肢作为推进力的来源。后肢细长，有明显的骨突（反映出强大的肌肉），表明恩氏古海豹在陆地上比现代鳍足类动物更活跃。
