Basilosaurus, the "King of Lizards"

Let’s travel back in time this month to visit our scary “scaley” friend, or so scientists thought! Get ready to meet our prehistoric predatory whale, Basilosaurus, “The King of Lizards”, or Zeuglodon.

Crdeit: Dominik Hammelsbruch – Own work (Wikipedia)

Following the bone trail…

1834 in Louisiana, American naturalist, and paleontologist, Richard Harlan (September 19, 1796 – September 30, 1843) received a single vertebra. He thought it came from a Plesiosuaurs-like creature. Harlan dubbed his findings as to the Basilosaurus, or “King Lizard.” In 1839, he took some more bones (jaws, teeth, etc.) to Sir Richard Owen (20 July 1804 – 18 December 1892) in England. He is an experienced comparative anatomist and paleontologist. He found that, in fact, these bones were mammalian in nature. The double-rooted teeth that gave it away.

He tried to have it renamed as Zeuglodon cetoides, to highlight its relationship to present-day whales. It didn’t stick, thus the name “King Lizard” still remains. Basilosaurus represents one of the earliest whales and descends from terrestrial mammals like the cetaceans we know today.

Living in the Eocene

These creatures roamed, well I suppose, swam the oceans about 40 million years ago, in the late Eocene Epoch. Little to no ice present on earth during the time they were prevalent. Found in the Gulf of Mexico, paleontologists found many of its fossils along the Mississippi and Alabama coast. Paleontologists found a smaller species of Basilosaurus in Egypt, B. isis, and in Pakistan.

Extending about 50-60 feet long, Basiloraurus was a slender and snake with a short rib cage. Its small pectoral fin-like appendages contained elbow joints, similar to those of sea lions. They had back flippers in place of what would have been their hind legs. Scientists think they utilized them during mating. They also noticed it had a small unattached pelvis. For more information, read our post on the evolution of early whales’ hips.

Though no substantial evidence, paleontologists have noted their tail vertebrae suggests the support for a tail fluke. However, it seems to be reduced, especially when comparing it to modern-day cetaceans. Basilosaurus’s body suggests it swam in an undulating motion. The remnants of where the muscles would have been placed showed a fragile connection. This means they did not deep dive, nor had high-speed chases to catch their prey. Their solid vertebrae most likely were fluid-filled.

Basilosaurus’s diet

It was one of the largest meat-eaters of its time. Due to skeletal evidence, looking at its large jaws and massive teeth, scientists think it was an apex predator of its time. “Stomach content,” looking at where Basiloraurus isis‘s stomach would have been, paleontologists found remains of baby Dorudons (another smaller whale ancestor) and larger fish.

Eocene seas. Featuring the early whales Basilosaurus and Dorudon – Credit: https://www.jameskuether.com/

The End of the King’s Reign…

Apart from that, not much is known about the rest of the Basilorurus‘ life history. With global cooling, which ended the Eocene Epoch, ocean circulations changed. This lead to the extinction of Basilosaurus and other archaic whales around that time frame (34 million years ago). With this new change, new currents and deep ocean upwellings helped diversify species of modern toothed and baleen whales.

Thanks for reading!!

For more literature on Basilosurus:

These Hips Don’t Lie! The Evolution of Whales

Naomi Mathew

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Naomi Mathew is a PhD student at University of Louisiana at Lafayette. She works on bioacoustics in marine mammals from the Gulf of Mexico. She is the co-founder of Whale Scientists. You can read more about her here