Why is it called Basilosaurus?

When first discovered, Basilosaurus fossils were mistaken for a giant sea serpent or reptile. The name means 'king lizard,' but it was later correctly identified as a whale.

Was Basilosaurus related to modern whales?

Yes. Basilosaurus was an early whale and part of the archaeocete group, which are ancestors of modern whales, dolphins, and porpoises.

Could Basilosaurus return today?

No, Basilosaurus is extinct. Its lineage evolved into modern whales, which are its living relatives.

Extinct Animals: Basilosaurus

Basilosaurus, an extinct, prehistoric whale that swam in the world’s oceans millions of years ago.

Basilosaurus (King Lizard)

Q: What is Basilosaurus?

Basilosaurus was an early whale that lived during the late Eocene epoch, about 40–34 million years ago. Despite its name, it was not a reptile but a fully aquatic mammal.

Q: How big was Basilosaurus?

Basilosaurus grew up to 15–20 meters (50–65 feet) long, with an elongated, serpentine body.

Q: What did Basilosaurus eat?

Basilosaurus preyed on fish, sharks, and smaller whales. Fossil evidence shows it had strong jaws and sharp teeth for slicing flesh.

Q: When did Basilosaurus go extinct?

Basilosaurus went extinct around 34 million years ago, during the transition from the Eocene to the Oligocene epoch.

$Highly detailed reconstruction of Basilosaurus swimming underwater in a sunlit ocean environment. The long, serpent-like prehistoric whale stretches horizontally across the frame, occupying the centre of the image. Its elongated body is smooth and streamlined, with a grey-blue coloration and subtle lighter markings along the underside. Small front flippers are visible near the head, while the tail tapers gradually, emphasising the animal’s distinctive, eel-like form. The head is narrow and elongated, with a tapered snout and small, forward-facing eyes. The surface of the skin appears smooth and slightly reflective, with shimmering light patterns created by sunlight refracting through the water above. The surrounding environment is a clear, open ocean with a deep blue gradient that darkens with depth. Above, the water’s surface is visible, with ripples and bright shafts of sunlight penetrating downward, illuminating the Basilosaurus and creating dappled highlights across its body. Small particles suspended in the water add to the sense of depth and realism. The composition emphasises movement and scale, with the creature gliding calmly through the water. The colour palette consists primarily of cool blues and soft silvery greys, contrasted by bright, white light rays from above.$ Basilosaurus

What is Basilosaurus?

Basilosaurus was a gigantic prehistoric whale that swam in the world’s oceans millions of years ago. It was one of the first fully aquatic whales and a top predator during its time.

How big was Basilosaurus?

Basilosaurus could grow up to 15–18 metres (49–59 feet) long. It weighed between 10 and 20 tonnes.

What did Basilosaurus eat?

Basilosaurus was a carnivore, preying on fish, sharks, and other marine mammals. Its long, conical teeth were perfect for grasping slippery prey and tearing flesh.

Basilosaurus appearance

Basilosaurus had a long, snake-like body with a small head, sharp teeth, and tiny, useless hind legs. Its body was slender compared to modern whales, making it look more like a sea serpent than today’s whales.

A realistic 3D model of a Basilosauruson a white background. Basilosaurus appearance

Where did Basilosaurus live?

Fossils of Basilosaurus have been found in North America, Northern Africa, and parts of the Middle East. It lived in warm, shallow seas that covered much of these regions during its era.

Interesting facts

Basilosaurus means "King Lizard" but it’s actually a mammal, not a lizard!
It was one of the first whales fully adapted to life in the water and could not live on land.
Basilosaurus had tiny, useless hind legs—leftovers from its land-dwelling ancestors.
It had a powerful bite and was the top predator in its ecosystem.
Despite its name, it was not a dinosaur or a reptile.

Basilosaurus Facts

Pronounced: bah-SIL-oh-SAW-rus

Name Means: "King Lizard"

Length: Up to 18 metres (59 feet)

Weight: Up to 20,000 kilograms (20 tonnes)

Diet: Carnivore (meat-eater)

Time: Eocene Epoch (about 41 to 34 million years ago)

Fossils Found: North America, Northern Africa, Middle East

Which family of animals did Basilosaurus belong to?

Basilosaurus belonged to the family Basilosauridae, ancient whales that were the first to live fully in the water. Modern whales, dolphins, and porpoises are distant relatives.

What other animals lived at the same time as Basilosaurus?

Basilosaurus shared its oceans with ancient sharks, early dolphins, sea turtles, and giant marine reptiles during the Eocene epoch.

Basilosaurus FAQ

Q1: What was Basilosaurus?

A1: Basilosaurus is an extinct species of giant whale that lived millions of years ago. It was a top predator in the ancient seas.

Q2: What did Basilosaurus look like?

A2: Basilosaurus had a long, snake-like body, sharp teeth, and tiny back legs that didn’t work. It looked very different from modern whales.

Q3: How big was Basilosaurus?

A3: It could grow up to 18 metres (59 feet) in length and weighed as much as 20 tonnes.

Q4: What did Basilosaurus eat?

A4: Basilosaurus hunted fish, sharks, and other marine mammals.

Q5: Where did Basilosaurus live?

A5: It lived in warm, shallow seas in what is now North America, Africa, and the Middle East.

Q6: When did Basilosaurus go extinct?

A6: Basilosaurus went extinct about 34 million years ago, as the climate changed and new types of whales evolved.

Q7: How strong was Basilosaurus’s bite?

A7: Its bite was powerful enough to crush bone and catch large prey, though not as strong as Megalodon's.

Q8: How is Basilosaurus related to modern animals?

A8: Basilosaurus is an ancient relative of today’s whales, dolphins, and porpoises.

Q9: Who discovered Basilosaurus?

A9: Fossilised bones of Basilosaurus were first discovered in the United States in the early 19th century. Scientists originally thought it was a giant lizard!

Q10: Are there any complete skeletons of Basilosaurus?

A10: Yes, several nearly complete skeletons have been found, including skulls, vertebrae, and even tiny hind limbs!

Generative AI Notiﬁcation: Some elements of this image have been created or enhanced using AI technology. To find out how we create all our prehistoric animals, click here.