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Basilosaurus cetoides and Dorudon atrox - Smithsonian | by Tim Evanson
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Basilosaurus cetoides and Dorudon atrox - Smithsonian

Skeleton of a basilosaurus cetoides in the Sant Hall of Oceans in the Smithsonian Museum of Natural History in Washington, D.C. The name Basilosaurus means "king lizard"; the animal is a mammal, but was originally thought to be a kind of dinosaur or lizard. The name "cetoides" means "whale-like."


Basilosaurus cetoides lived 40 to 34 million years in warm seas around the world. It was first discovered in Louisiana in 1832. Skeletons were so common, people used them for chairs! Fossils have since been found in Pakistan and Egypt, and scientists think there may be anywhere from 3 to nine sub-species.


Basilosaurus cetoides grew to be about 60 feet (18 m) in length and was the largest animal on land or sea living at the time. The animal was extremely elongated. with the body behind the tail tapering rapidly. The bones at the tip of the tail indicate it had a very small fluke for its massive size. From the way the muscles appear to attach to the spine, the amazing flexibility of the spine, and other features, it's clear that basilosaurus cetoides used its whole body (not just the tail) to move through the water. It was much like an eel, although eels move sinuously side-to-side and the basilosaurus cetoides moved up and down!


Basilosaurus cetoides probably had a small dorsal fin or ridge, and had extremely tiny two foot (0.6 m) long hind limbs. These limbs had limited mobility, and in fact could only assume two positions: Against the body and against the belly. Scientists think that the limbs were used during sex, to help the male cling to the female.


The bones of basilosaurus cetoides were hollow and probably filled with fluid. This helped it maintain buoyancy in the ocean, and has led scientists to conclude that it did not dive much (if at all). It probably could not move very fast or for very long, and probably lurked at the surface as an ambush hunter. The brain in basilosaurus cetoides is quite small, which means it was probably a solitary animal. There is also no indication that it could echolocate like modern whales.


This skeleton in the Smithsonian is the only real specimen currently exhibited anywhere in the world.


Toward the end of the tail of the basilosaurus cetoides can be seen the skeleton of a dorudon atrox, another ancient whale. Overhead is the skull of a modern right whale. To the right is the skull of a juvenile right whale, and to the lower right is the skull of a llanocetus denticrenatus (an ancient precursor to the baleen whales).

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Taken on January 7, 2012