 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 . 
