Produced by the Population Genetics and Evolution class, Furman University

The Paleogene: Basilosaurus
Basilosaurus is (“king lizard”) was an early cetacean that was first discovered in Louisiana by Dr. Richard Harlan, who erroneously classified it as a marine reptile in 1843. Richard Owen was the first to correct Harlan’s error, renaming the specimen Zeuglodon (“yoked tooth”). Due to taxonomic conventions, however, the misleading name Basilosaurus remains (Waggoner 2001). Basilosaurus featured an exceptionally long body; males measured up to 18 m long and the females reached about 15 m. The compressed vertebrae in its tail suggest that this arachaeocete may have had a tail fluke. However, since this fluke is at the end of an extremely long tail, it most likely provided only minimal locomotion. Since Basilosaurus lacked the adaptations necessary for deep diving and could not hold its breath for very long, researchers have concluded that it most likely swam near the surface. Basilosaurus possessed several key traits that differentiate it from modern whales. It had nostrils at the end of its snout instead of a blowhole, had a relatively small brain, and lacked the echolocation system characteristic of some modern whales and dolphins (BBC 2008). The discovery that Basilosaurus had small, functional pelvic limbs as well as foot bones is of particular evolutionary significance because it helps place archaeocetes between Paleocene land mammals that clearly used hind limbs for locomotion and the more recent Oligocene whales that lacked functional pelvic limbs (Gigerich et al. 1990).

Page by Robert Mazgaj
Basilosaurus. From: University Museum of Paleontology,Photo Credit: Mark Uhen, Cranbrook Institute of Science

BBC. 2008. Basilosaurus. Accessed April 12, 2010.

Gingerich PD, Smith BH, Simons EL. 1990. Hind limbs of Eocene Basilosaurus: evidence of feet in whales. Science 249: 154-157.

Waggoner B. 2001. Introduction to the Cetacea. University of California Museum of Paleontology. Accessed April 12, 2010.