and South Carolina in the United States. The type species D. serratus was, and still is, based solely on two partial maxillae with a few teeth, cranial fragments, and a dozen vertebrae with some additional material, collected but not described by Gibbes, and referred to the type species. Before Uhen 2004, D. atrox was based solely on Andrews holotype skull, lower jaw, and the vertebrae he referred to it, but is now the best known archaeocete species. The two species of Dorudon differ from other members of Dorudontinae mainly in size: they are considerably larger than Saghacetus and slightly larger than Zygorhiza, but also differ from both these genera in dental and/or cranial morphology. The limited known material for D. serratus makes it difficult to compare the two species of Dorudon. placed D. atrox in the same genus as D. serratus because of similarities in size and morphology, but kept them as separate species because of differences in dental morphology. Even-though D. serratus is the type species, the description of Dorudon is largely based on D. atrox because of its completeness. The cranial morphology of D. atrox makes it distinct from all other archaeocetes. Description Dorudon was a medium-sized whale, with D. atrox reaching in length and in body mass. Dorudontines were originally believed to be juvenile individuals of Basilosaurus as their fossils are similar but smaller. They have since been shown to be a different genus with the discovery of Dorudon juveniles. Although they look very much like modern whales, basilosaurines and dorudontines lacked the 'melon organ' that allows their descendants to use echolocation as effectively as modern whales. Like other basilosaurids, their nostrils were midway from the snout to the top of the head. Dentition The dental formula for Dorudon atrox is . Typical for cetaceans, the upper incisors are aligned with the cheek teeth, and, except the small I1, separated by large diastemata containing pits into which the lower incisors fit. The upper incisors are simple conical teeth with a single root, lacking accessory denticles, and difficult to distinguish from lower incisors. The upper incisors are missing in most specimens and are only known from two specimens. The upper canine is a little larger than the upper incisors, and, like them, directed slightly buccally and mesially. P1, only preserved in a single specimen, is the only single-rooted upper premolar. Apparently, P1 is conical, smaller than the remaining