Basilosaurus cetoides skeleton
|Species|| B. cetoides|
Basilosaurus ("King Lizard") is a genus of cetacean that lived 40 to 34 million years ago in the Late Eocene. Its fossilized remains were first discovered in the southern United States (Louisiana). The American fossils were initially believed to be some sort of reptile, hence the suffix -"saurus", but later found to be a marine mammal. Richard Owen wished to rename the creature Zeuglodon ("Yoked Tooth"), but, per taxonomic rules, the creature's first name remained permanent. Fossils from at least two other species of this taxon have been found in Egypt and Pakistan. Basilosaurus averaged about 18 metres (60 ft) in length, and is believed to have been the largest animal to have lived in its time. It displayed an unparalleled degree of elongation compared with modern whales. Their very small vestigial hind limbs have also been a matter of interest for paleontologists. The species B. cetoides is the state fossil of Mississippi and Alabama in the United States.
Basilosaurus was highly elongated due to the unparalleled elongation of its vertebrae. The skeletal anatomy of the tail suggests that a small fluke was probably present, which would have aided only vertical motion. Most reconstructions show a small, speculative dorsal fin similar to a rorqual whale’s, but other reconstructions show a dorsal ridge. The whale also possessed small, 0.6 meter (2 ft) hind limbs, which clearly could not aid locomotion on a 15–22 meter (50–72 foot) animal. At one time, it was believed that Basilosaurus had some sort of armor plating, but subsequent research has refuted this interpretation.
Analysis has shown that the reduced limbs could rapidly adduct between only two positions. It is also believed that Basilosaurus relied on unusual modes of locomotion, relative to other cetaceans; similarly sized thoracic, lumbar, sacral and caudal vertebrae imply that it moved in an anguilliform (eel-like) fashion, but predominantly in the vertical plane. Paleontologist Philip Gingerich theorized that Basilosaurus may also have moved in a very odd, horizontal anguilliform fashion to some degree, something completely unknown in modern cetaceans.
The vertebrae of the whale appear to have been hollow, and it is likely that they were also fluid-filled. This would imply that Basilosaurus typically functioned in only two dimensions at the ocean surface, compared with the three dimensional habits of most other cetaceans. Judging from the relatively weak axial musculature and the thick bones in the limbs, Basilosaurus is not believed to have been capable of sustained swimming or deep diving. It is also believed that the primitive whale was incapable of terrestrial locomotion.
The head of Basilosaurus did not have room for a melon like modern day toothed whales, and the brain was smaller in comparison as well. It is believed that they therefore did not have the social capabilities of modern whales.
During the early 19th century, Basilosaurus cetoides fossils were so common (and sufficiently large) that they were regularly used as furniture in the American south. Vertebrae were sent to the American Philosophical Society by a Judge Bly of Arkansas and Judge John Creagh of Clarke County, Alabama. Both fossils ended up in the hands of the anatomist Dr. Richard Harlan, who requested more examples from Creagh. With some reservation, Harlan speculated that the fossils belonged to a (50 m [166 ft] long) marine reptile, for which he suggested the name Basilosaurus, meaning “King reptile”.
When the British anatomist Sir Richard Owen studied the spine, mandibular fragments, arms, and ribs (more recently found), he proclaimed them to be mammalian. Owen proposed renaming the find to Zeuglodon cetoides (“whale-like yoke teeth”), which is now a junior synonym; though the latter is considered by many to be a more fitting name, the first-published name always takes precedence. The name Zeuglodon refers to the double rooted teeth typical of marine mammals.
In 1845, Dr. Albert Koch heard stories of giant bones in Alabama, and later traveled there to cobble together a full skeleton. He eventually reconstructed a huge 114-foot (35 m) skeleton of a “sea serpent” he called "Hydrarchos", which he displayed in New York City, and later Europe. It was eventually shown to have come from five different individuals, some of which were not Basilosaurus. The remains were eventually destroyed in the Great Chicago Fire.
In 1894, Smithsonian curator Charles Schuchert went to Alabama and collected fossil bones in order to mount the first scientifically accurate specimen. The mount has been altered several times in response to new discoveries. It is still on display in the National Museum of Natural History, the only real specimen currently exhibited in the world. There is a plaster cast on display in the Alabama Museum of Natural History.
Fossil finds of a related species, Basilosaurus isis, have been found in the aptly named Valley of the Whales in Egypt. The fossils were very well preserved, hind limbs included, and were rather numerous. Paleontologist Philip Gingerich, who organized several expeditions to the valley, speculated that Egyptian crocodile worship may have been inspired by the huge skeletons that lay there. Fossil remains of another species, Basilosaurus drazindai, have been found in Pakistan. Another fossilized species, Basiloterus husseini, was its closest known relative, but was neither as large nor as elongated.