这个词是什么意思？
An order of heavy-bodied, slow-moving, completely aquatic, herbivorous mammals. The body is fusiform, plump, and hairless, except for bristles on the snout. Hindlimbs are absent, the forelimbs are modified to flippers, and the tail is a horizontal fluke. (From Scott, Concise Encyclopedia Biology, 1996)
中文名称索引；定义为 MeSH 英文原文，尚未逐条译审。MESH:D020453 · MeSH 2026。
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