Basilosaurid

Systematics and Classification

Although Basilosauridae is historically recovered as a monophyletic group sister to Neoceti, more recent studies have shown that Basilosauridae may instead represent a paraphyletic grade that gave rise to modern whales. The inner systematics of Basilosauridae as a whole are also under revision. Recent analyses have shown that large body size and vertebral elongation are traits that can evolve convergently among these whales, making these traits poor indicators of their true relationships. As of the description of Tutcetus, all fully aquatic whales fall into a larger clade known as Pelagiceti, of which the poorly known cetacean Eocetus is the basalmost member. From there, there are three major clades that are recovered. One clade contains the diminutive basilosaurids Tutcetus, Chrysocetus, and Ocucajea. Another contains Basilosaurus and several taxa typically regarded as dorudontines, such as Dorudon, Zygorhiza, and the large Cynthiacetus. The final clade contains a monophyletic Pachycetinae sister to Neoceti, with Supayacetus as the most basal member of the Pachycetinae clade. The results of this analysis are shown below.