More than Just Old Bones: The Fossil Record Informs us About Homology, and Convergences of Anatomy, Physiology and Behavior in the Cetacea otherwise Unknown from Modern Animals pp. 129-140
Authors: (Brian Lee Beatty, Alton C. Dooley, Jr., Department of Anatomy, New York College of Osteopathic Medicine, Old Westbury, New Cork, USA, and others)
Abstract: The biology of cetaceans is one of the most compelling because of the extreme adaptations whales and dolphins have had to evolve to manage a life in water. The fossil record of cetaceans is rich, and though much attention has been given to the origins of whales from terrestrial artiodactyls, it is important to realize that the biology, physiology, and behavior of modern cetaceans has not remained unchanged since this initial transition to being aquatic. Here I review some examples of how the fossil record of cetaceans informs us of how the evolution of anatomy, physiology and behavior has diverged and converged between and within the Odontoceti and Mysticeti in ways that would not be known if one were only to study their living representatives. Studies of paleopathologies associated with decompression syndrome inform us that odontocetes and mysticetes independently evolved specializations for repetitive deep diving. Cross sectional anatomy of ribs from modern and fossil mysticetes indicates that mysticetes started out with hyperdense skeleton and were probably benthic feeding, only to converge on the osteoporosis-like state found among most modern mysticetes and odontocetes. In the end, these studies of fossil cetaceans highlight the fact that many of our assumptions about homologies of anatomy, physiology, and behavior in modern cetaceans may be misled by only studying modern cetaceans, and that interpretations of modern animal biological data that rely on these sorts of assumptions should be reconsidered.