Basilosaurus was the first whale to become truly gigantic in size. Their large bulk meant they needed a great deal of food to keep them going and it is thought that most Basilosaurus spent their days swimming slowly through the shallows, watching for potential prey.

Basilosaurus was not a particularly fussy eater. Fish, sharks, squid, turtles and other marine mammals were all a staple part of its diet and Basilosaurus was well-equipped to find and tackle prey with its keen eyesight and hearing.

Like modern whales, Basilosaurus was an air breather and could not have stayed underwater for long periods of time. It would have to return to the surface to breathe but Basilosaurus did not have a blow hole, it would have to raise the tip of its nose out of the water so that the nostrils could take deep breaths

Basilosaurus ("King Lizard") was a genus of cetacean that lived from 40 to 37 million years ago in the Eocene. Its fossilized remains were first discovered in the southern United States (Alabama), and were initially believed to be some sort of reptilian sea monster, hence the suffix -"saurus". Fossils from at least two other species of this taxon have been found in Egypt and Pakistan. Basilosaurus averaged about 18 meters (60 feet) in length, and displayed an unparalleled degree of elongation compared with modern whales. Their very small vestigial hind limbs have also been a matter of interest for paleontologists. The species is the state fossil of Alabama.