Basilosaurus

Basilosaurus, whose name translates to "king lizard," is a genus of large, predatory prehistoric whale that lived during the late Eocene, between about 41.3 and 33.9 million years ago. It was the first archaeocete and the first prehistoric whale ever described by scientists, in 1834. The name came from an early mistake: the fossils were thought to belong to a giant reptile. Later research showed the animal was actually an early marine mammal, but because of the rules of zoological nomenclature, the original name stuck.

The type species, *B. cetoides*, was discovered in the southeastern United States. A second species, *B. isis*, was named in 1904 and lived in what is now the Mediterranean region, with fossils found in North Africa and Jordan. *Basilosaurus* is considered one of the largest animals of the Paleogene era. The type species reached about 17 to 20 meters (56–66 feet) in length and weighed up to 15 metric tons (17 short tons). It was the top predator in the shallow inland seas, hunting sharks, large fish, and other marine mammals. Stomach contents and bite marks on the skulls of the smaller, dolphin-like *Dorudon* suggest that *Dorudon* was a major food source.

For a time, *Basilosaurus* served as a wastebasket taxon, with many different Eocene cetaceans assigned to the genus. Most of those assignments have since been invalidated or reclassified under other genera, leaving only two confirmed species. *Basilosaurus* may have been one of the first fully aquatic whales, sometimes grouped under the name Pelagiceti. Unlike modern whales, it had a variety of tooth types—including canines and molars—and was probably able to chew its food, whereas modern cetaceans swallow their prey whole.

The first remains of *B. cetoides* were found in Ouachita Parish, Louisiana, in the Yazoo Clay formation. Vertebrae were sent to the American Philosophical Society by Judge Henry Bry of Louisiana and Judge John Creagh of Alabama. Both sets of fossils ended up with anatomist Richard Harlan, who asked for more. The bones were discovered after rain caused a hillside of sea shells to slide, revealing a curved line of bones "measuring upwards of four hundred feet [120 m] in length, with intervals which were vacant." Many of these bones were used as andirons and destroyed; Bry saved what he could, but believed more remained. He thought the bones belonged to a "sea monster"