An early whale, Basilosaurus is a relative of (but not an ancestor to) modern ceteaceans.

Meaning of scientific name
"king lizard".

Pronunciation of scientific name
BASS-il-oh-SAWR-uss

Statistics
Females around 15m long, males around 18m long.

Physical description
This early cetacean (a member of the whale family) is well known from a large number of fossils. Two species are known, and they were clearly common in the Eocene seas. Its enormously long body has presented a puzzle for scientists studying its movement. The vertebrae at the end of its tail seem to be compressed, as they are in animals that have a tail fluke, but having the fluke at the end of such a long tail would make it very inefficient. Its long tail must have been full of muscle in order to power the fluke, unlike some drawings which show it thin and snake-like. It had nostrils at the end of its snout, rather than a blow-hole as modern whales and dolphins do. They had tiny limbs, a reminder of its land mammal ancestors.

Distribution
The first Basilosaurus fossils were found in Louisiana, USA, but another species was soon discovered preserved in large numbers in the Fayum deposits of Egypt.

Habitat
They ived in the shallow warm seas around the world.

Diet
Basilosaurus were carnivorous, feeding on fish, sharks, molluscs and other cetaceans (whales and dolphins).

Behaviour
Basilosaurus was obviously a predator as fossils have been found with balls of fish and small sharks inside. It was not adapted for deep diving, and would not have been able to hold its breath for very long underwater so it must have swum quite near the surface. It did not have the echolocation system of some modern whales and dolphins, nor the large brain.

Reproduction
No juvenile Basilosaurus have ever been found, suggesting that they gave birth in the open ocean or a region where fossils have not yet been discovered.

Conservation status
Extinct.

History
This early cetacean (a member of the whale family) is a descendant of some of the early carnivorous hoofed animals via amphibious animals like Ambulocetus. They lived 40-36 million years ago.

Best place to see
New Walk Museum; Ipswich Museums Service; Natural History Museum.