A pair of the early whales known as Basilosaurus


Basilosaurus fossils were first discovered in Louisiana, USA in the 1830s. Believed to be giant reptilian sea monsters, they were named Basilosaurus, or 'king lizards'. Later, they were shown not to be reptilian but gigantic, ancient whales. They were more elongated than modern whales and had a pair of small legs, that could have been a hangover from their terrestrial ancestry. A large number of fossils of these marine predators has been found to date, leading to the conclusion that Basilosaurus were common in the warm shallow seas of the time.

Scientific name: Basilosaurus

Rank: Genus

Common names:

king lizard

Watch video clips from past programmes (4 clips)

In order to see this content you need to have an up-to-date version of Flash installed and Javascript turned on.


Discover what these behaviours are and how different plants and animals use them.

Additional data source: Animal Diversity Web

When they lived

Discover the other animals and plants that lived during the following geological time periods.

Eocene epoch Eocene epoch
The Eocene began as a time of global warming, with temperatures across the planet soaring. Forests thrived and trees grew even in polar regions.