 Both basilosaurids and dorudontines are relatively closely related to modern cetaceans , which belong to parvorders Odontoceti and Mysticeti . However , according to a 1994 study done by Fordyce and Barnes , the large size and elongated vertebral body of basilosaurids preclude them from being ancestral to extant forms . As for dorudontines , there are some species within the family that do not have elongated vertebral bodies , which might be the immediate ancestors of Odontoceti and Mysticeti . The other basilosaurids became extinct . 
