10 Facts About Basilosaurus

Meet the So-Called King Lizard

The skull of a <i>Basilosaurus</i> on display
The skull of a Basilosaurus on display. Wikimedia Commons

One of the first identified prehistoric whales, Basilosaurus, the "king lizard," has been a part of American culture for literally hundreds of years, especially in the southeastern U.S. Discover fascinating details about this enormous marine mammal.

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Basilosaurus Was Once Mistaken for a Prehistoric Reptile

An illustration of the <i>Basilosaurus</i>
An illustration of the Basilosaurus. Wikimedia Commons

In the early 19th century, when the fossil remains of Basilosaurus were being studied by American paleontologists, there was a great deal of interest in giant marine reptiles like Mosasaurus and Pliosaurus (which had recently been discovered in Europe). Because its long, narrow skull so closely resembled that of Mosasaurus, Basilosaurus was initially and incorrectly "diagnosed" as a marine reptile of the Mesozoic Era and given its deceptive name (Greek for "king lizard") by the naturalist Richard Harlan.

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Basilosaurus Had a Long, Eel-Like Body

A museum display of a <i>Basilosaurus</i> skeleton. It's attached to the ceiling to give it the impression of swimming
Museum display of a Basilosaurus skeleton. Wikimedia Commons

Unusually for a prehistoric whale, Basilosaurus was sleek and eel-like, measuring up to 65 feet long from the tip of its head to the end of its tail fin but only weighing in the neighborhood of five to 10 tons. Some paleontologists speculate that Basilosaurus both looked and swam like a giant eel, undulating its long, narrow, muscular body close to the water's surface. This, however, would place it so far outside the mainstream of cetacean evolution that other experts remain skeptical.

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The Brain of Basilosaurus Was Comparatively Small

A <i>Basilosaurus</i> skeleton swoops down from the ceiling with arched back and mouth wide open at the French National Museum of Natural History in Paris
A Basilosaurus skeleton swoops down from the ceiling with arched back and mouth wide open at the French National Museum of Natural History in Paris. Wikimedia Commons

Basilosaurus plied the world's seas during the late Eocene epoch, about 40 to 34 million years ago, at a time when many megafauna mammals (like the terrestrial predator Andrewsarchus) were endowed with giant sizes and comparatively small brains. Given its enormous bulk, Basilosaurus possessed a smaller-than-usual brain, a hint that it was incapable of the social, pod-swimming behavior characteristic of modern whales (and perhaps also incapable of echolocation and the generation of high-frequency whale calls).

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Basilosaurus Bones Were Once Used as Furniture

Pencil drawing of a fossilized <i>Basilosaurus</i> bone that would have been used as furniture
Pencil drawing of a fossilized Basilosaurus bone that would have been used as furniture. Wikimedia Commons

Although Basilosaurus was only officially named in the early 18th century, its fossils had been extant for decades—and were used by residents of the southeastern U.S. as andirons for fireplaces or foundation posts for houses. At the time, of course, no one knew that these petrified artifacts were actually the bones of a long-extinct prehistoric whale.

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Basilosaurus Was Once Known as Zeuglodon

An artist's rendering of the Zeuglodon.

Although Richard Harlan came up with the name Basilosaurus, it was the famous English naturalist Richard Owen who recognized that this prehistoric creature was actually a whale. It was Owen, therefore, who suggested the slightly comical name Zeuglodon ("yoke tooth") instead. Over the next few decades, various specimens of Basilosaurus were assigned as species of Zeuglodon, most of which either reverted back to Basilosaurus or received new genus designations (Saghacetus and Dorudon being two notable examples).

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Basilosaurus Is the State Fossil of Mississippi and Alabama

An illustration of a pair of <i>Basilosauruses</i> above a seafloor
An illustration of a pair of Basilosauruses above a seafloor.

ThoughtCo / Nobu Tamura

It's unusual for two states to share the same official fossil; it's even rarer for these two states to border each other. Be that as it may, Basilosaurus is the official state fossil of both Mississippi and Alabama (at least Mississippi divides the honor between Basilosaurus and another prehistoric whale, Zygorhiza). It would be reasonable to infer from this fact that Basilosaurus was native to North America exclusively, but fossil specimens of this whale have been discovered as far afield as Egypt and Jordan.

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Basilosaurus Was the Inspiration for the Hydrarchos Fossil Hoax

Illustration of the 1845 exhibit of a sea monster known as Hydrarchos, which was reported as fake
Illustration of the 1845 exhibit of a sea monster known as Hydrarchos, which was reported as fake.

Wikimedia Commons / Public Domain

In 1845, a man named Albert Koch perpetrated one of the most notorious hoaxes in the history of paleontology, reassembling a bunch of Basilosaurus bones into a fraudulent "sea monster" named Hydrarchos ("ruler of the waves"). Koch exhibited the 114-foot long skeleton in a saloon (the price of admission: 25 cents), but his scam imploded when naturalists noticed the different ages, and provenances, of Hydrarchos' teeth (specifically, a mixture of reptilian and mammalian teeth, as well as teeth belonging to both juveniles and full-grown adults).

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The Front Flippers of Basilosaurus Retained Their Elbow Hinges

Artist rendering of a <i>Basilosaurus</i> with its flippers
Artist rendering of a Basilosaurus with its flippers.

ThoughtCo / Dmitry Bogdanov

As huge as Basilosaurus was, it still occupied a fairly low branch on the whale evolutionary tree, plying the oceans only 10 million years or so after its earliest ancestors (such as Pakicetus) were still walking on land. This explains the unusual length and flexibility of Basilosaurus' front flippers, which retained their rudimentary elbows. This feature disappeared entirely in later whales and is today retained only by the distantly related marine mammals known as pinnipeds.

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The Vertebrae of Basilosaurus Were Filled With Fluid

An illustration of the <i>Basilosaurus</i> showing a mouthful of teeth
An illustration of the Basilosaurus showing a mouthful of teeth.

ThoughtCo / Nobu Tamura

One unusual feature of Basilosaurus is that its vertebrae were not made of solid bone (as is the case with modern whales) but were hollow and filled with fluid. This is a clear indication that this prehistoric whale spent most of its life near the water's surface since its hollow backbone would have crumpled from the intense water pressure deep beneath the waves. Combined with its eel-like torso, this anatomical quirk tells us a lot about Basilosaurus' preferred hunting style.

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Basilosaurus Wasn't the Largest Whale That Ever Lived

An illustration showing the size of an average human next to a 50-ton Leviathan killer whale
An illustration showing the size of an average human next to a 50-ton Leviathan killer whale.

ThoughtCo / Sameer Prehistorica

The name "King Lizard" is misleading in not one, but two, ways: Not only was Basilosaurus a whale rather than a reptile, but it wasn't even close to being the king of the whales; later cetaceans were much more formidable. A good example is the giant killer whale Leviathan (Livyatan), which lived about 25 million years later (during the Miocene epoch), weighed as much as 50 tons, and made a worthy opponent for the contemporaneous prehistoric shark Megalodon.

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Strauss, Bob. "10 Facts About Basilosaurus." ThoughtCo, Feb. 16, 2021, thoughtco.com/facts-about-basilosaurus-king-lizard-whale-1093325. Strauss, Bob. (2021, February 16). 10 Facts About Basilosaurus. Retrieved from https://www.thoughtco.com/facts-about-basilosaurus-king-lizard-whale-1093325 Strauss, Bob. "10 Facts About Basilosaurus." ThoughtCo. https://www.thoughtco.com/facts-about-basilosaurus-king-lizard-whale-1093325 (accessed June 7, 2023).