section_path: Vertebrate skeletons/Mammals/Marine mammals
section_name: Marine mammals
paragraph_text: Marine mammals
  
  To facilitate the movement of marine mammals in water, the hind legs were either lost altogether, as in the whales and manatees, or united in a single tail fin as in the pinnipeds (seals). In the whale, the cervical vertebrae are typically fused, an adaptation trading flexibility for stability during swimming.