Some protocetids had short, wide fore- and hindlimbs that were likely to have been used in swimming, but the limbs gave a slow and cumbersome locomotion on land. It is possible that some protocetids had flukes. However, it is clear that they were adapted even further to an aquatic life-style. In "Rodhocetus", for example, the sacrum (a bone that, in land-mammals, is a fusion of five vertebrae that connects the pelvis with the rest of the vertebral column) was divided into loose vertebrae. However, the pelvis was still connected to one of the sacral vertebrae. The ungulate ancestry of these archaeocetes is still underlined by characteristics like the presence of hooves at the ends of the toes in "Rodhocetus".