Much of my current research is focused on the early evolution of cetaceans (whales and dolphins). Modern cetaceans are fully aquatic mammals that have no hind limbs, flippers for forelimbs, and fusiform bodies, among other traits. I am very interested in the evolutionary development of these aquatic attributes. Before describing my research in particular, a little background information is necessary.

Modern cetaceans are divided into two groups. Odontoceti (toothed whales) are the toothed whales. These include dolphins, porpoises, beaked whales, sperm whales, narwhals, and others. These cetaceans often have teeth that are simple pegs (or other forms that are nevertheless highly modified from early mammal teeth). Odontocetes also use echolocation to find their prey and to sense their surroundings underwater. Mysticeti (mustached whales) are the baleen whales. These animals have no teeth but rather have structures that hang from their upper jaws that they use to filter food from the water. These structures are made of baleen, which is composed of the same material as your fingernails.

Fossil representatives of these modern groups go back to the Oligocene epoch. Early members of these groups are more primitive than the modern representatives (odontocetes with primitive-looking teeth, mysticetes with teeth), but they are part of these modern groups. Prior to the Oligocene, during the Eocene epoch, there were no odontocetes or mysticetes, only Archaeocetes (ancient whales). Archaeocetes retain many features of more primitive mammals in their skulls, teeth, vertebral columns, and limbs relative to their modern descendants. My research has focused on archaeocetes from the middle and late Eocene, protocetid and Basilosaurids.

The type specimen of Eocetus wardii includes thoracic and lumbar vertebrae, ribs, a piece of the snout, and much of the right innominate. The lumbar vertebrae of Eocetus are interesting in that they are somewhat elongate, not unlike those of later Basilosaurus. Also, the exterior texture of the bone is "pock marked" with the openings of tiny vascular canals that feed into the multiple layers of cortical bone. Similar texture can be seen in specimens of Basilosaurus. Features like this might lead one to think they are related, but the innominate of Eocetus is quite different from that of Basilosaurus, and the type specimen of Eocetus (Eocetus schweinfurthi) shows that the teeth of Eocetus are like those of other protocetids, rather than like those of basilosaurids (see below).

Basilosaurids are the youngest group of archaeocete whales. By the late Eocene, all other groups of archaeocetes became extinct and only basilosaurids. Based on this observation and the sharing of many derived morphological features with early mysticetes and early odontocetes, basilosaurids are thought to have given rise to modern cetaceans. Basilosaurids all share the loss of the third upper molar, the presence of accessory denticles on their cheek teeth, a high number of lumbar vertebrae, highly reduced hind limbs that do not have a bony connection to the vertebral column, and dorsoventrally flattened tail vertebrae indicating the presence of a tail fluke.