Prehistoric Earth: A Natural History Wiki

This is the monster that we're looking for: Basilosaurus. That name means "King Lizard". 18 meters of predatory whale. Four times the length of a great white shark, these whales weigh 60 tons.
— Allen, about Basilosaurus
in Big Blue Killer Whale

Basilosaurus (name meaning "King Lizard"), often nicknamed the "Big Blue Killer Whale" by Rebecca, is a genus of large, serpentine-like archaeocete that originated during the Late Eocene epoch in what is now Africa. Originally believed to be a reptilian sea serpent, it was later discovered to be a primitive whale. Measuring 18 meters long, weighing 60 tons, and possessing a long slender body akin to a serpent, Basilosaurus was the apex predator in the Tethys ocean during its existence and was one of the first in the line of giant cetaceans.

In the Series 3 episode "Big Blue Killer Whale," a mating pair of Basilosaurus was brought back to the park from Eocene Egypt, 36 million years ago. They currently reside in the Whale Watching enclosure and are one of the park's largest marine animals. The female eventually gave birth to a healthy male calf.


Era & Discovery[]

Basilosaurus lived in the oceans during the Late Eocene period from 41 to 33 million years ago. The apex predator of the Eocene seas, they evolved from small fury tree-dwelling creatures. The end of the Eocene had been brought to the brink of great climatic change. As the Oligocene began, Basilosaurus vanished and fell victim to the climatic shifts that ended the Eocene, changing the warm sea into a cold ocean and causing the Tethys Sea to disappear.

Basilosaurus skeleton

First discovered in Egypt in the year 1839 by Charles William Andrews, Basilosaurus was the oldest-known fossilized cetacean (or whale) for many decades. Its tiny back legs were seen as proof that the whales were once land animals, but it was not until the discovery of 'walking whales', such as Ambulocetus, that there was proof of this. It is now known that the whales evolved from large, crocodile-like animals called mesonychians such as Andrewsarchus.

Because its name "Basilosaurus" means "King Lizard," when the fossils were first discovered in 1832, Basilosaurus was originally thought by paleontologists to have been giant marine reptiles, much like the Mosasaurs and Plesiosaurs of the Mesozoic Era, especially according to an artist drawing of them in 1960. But instead, they were eventually found out to be a primitive species of whales.

Physical Attributes[]

By far the largest predators in the Eocene seas, Basilosaurus were large, carnivorous whales well over four times the length of a great white shark. Measuring 49 – 66 feet (15 – 20 m) long and weighing up to 60 tons (132,000 lbs.), Basilosaurus was one of the largest carnivorous animals the world had ever known. It's incredible to think, then, their ancestors were tiny, furry, shrew-like animals that lived in trees. On average, Basilosaurus ate 80 kilograms of food every day.

It also had a streamlined, serpentine body shape with was useful in making it a swift and deadly predator. Basilosaurus had small hind paddles, which were useless for aiding in locomotion but were extremely important during copulation. Because so, some scientists akin Basilosaurus to sea serpents. It also had a long and strong fluke used to propel its weight and size through the water. Basilosaurus had light blue skin on its back and white skin on its underside. Because of this, Rebecca often nicknames Basilosaurus the "big blue killer whale," which is also the title of the second episode of Series 3.

Basilosaurus killing a Dorudon

However, it is the skull of Basilosaurus that is chilling. There is not a species of whale that has a skull-like that of Basilosaurus in modern times, not even toothed whales. It had a very large skull with strong jaws, which were lined with large teeth used to severely injure its victim. There were large peg-like teeth at the front for seizing prey. Once inside the mouth, the prey was sliced up by the large teeth at the back, great big cusps at the front. They were for slicing through flesh.

Behavior & Traits[]

Basilosaurus was a solitary animal and as such, it would have spent long periods of time on its own. Unlike most of the modern species of cetaceans, the interaction between Basilosaurus was often hostile and lethal. Basilosaurus lacked a 'melon', the organ that modern whales and dolphins use for echolocation as well as the ability to 'sing' to one another. Even though Basilosaurus couldn't sing, the only time the males and females would interact was during courtship. During these mating competitions, female Basilosaurus were eagerly pressured by several males, but it was the largest and oldest male that won the right to mate with the target female. Mating was not an easy task for such huge, free-floating animals. So Basilosaurus needed a little extra help.

Basilosaurus mating

As the successful male maneuvered into position, given their sinuous body shape, these whales called upon a relic of their distant land-living ancestors. Both a memento of its land-dwelling ancestors and a useful tool during copulation, Basilosaurus retained two, small hind flippers, or "back limbs". Due to their tiny size, they were useless as a means of walking or even steering while swimming. However, during mating, they were used to lock their long narrow bodies onto each other, guiding one another into the correct mating position during mating.

Like all whales, Basilosaurus was an air breather, however, it did not possess a blow-hole. Instead, it had to raise the tip of its nose out of the water to take a breath. Its ribcage was solid and not very flexible, which meant that its lung space was restricted; thus Basilosaurus could not stay underwater for prolonged periods of time. Any attacks it made, therefore, had to be swift and accurate. With its high mammalian metabolism, Basilosaurus would have needed to eat, on average, 80 kilograms of food every day in order to keep its energy reserves high.

Basilosaurus lived in most of the warm seas around the world. It did not have the large insulating fat deposits of modern whales, so it could not have strayed into cooler waters. It was therefore restricted mainly to warmer waters, such as the ancient Tethys Sea that once ran between the African and European continents.

Easily being the largest predator of its time, Basilosaurus was a deadly predator and was capable of attacking large prey, including other whales, such as its smaller relative - Dorudon. When it came to food, Basilosaurus was not a fussy eater. Its favored prey Dorudon, but its diet also extended to fish, sharks, squid, turtles, and other marine mammals, such as primitive proboscideans like Moeritherium which lived in the shallow mangrove swamps as well as other types of marine animal could all fall prey to the keen eyesight of Basilosaurus. It would swim in pursuit of its victims, using its powerful serpentine tail to make brief but fast pursuits. Once its powerful jaws and sharp, serrated teeth clamped down on to an animal, there could be no escape.



  • Basilosaurus is the first and largest prehistoric whale brought to the park.
  • Due to its blue coloring, the female Basilosaurus portrayed in the series is given a nickname by Rebecca: the "big blue killer whale".
  • Basilosaurus does have the typical whale sounds but also was given additional roars, such as crocodile, seal, and walrus sound effects to give it a more intimidating presence.