Basilosaurus
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Basilosaurus was a genus of cetacean that lived from 40 to 37 million years ago in the Eocene. Its fossilized remains were first discovered in the American South, and were initially believed to be some sort of reptilian sea monster, hence the suffix "saurus". Fossil from at least two other species have been found in Egypt and Pakistan. They were at least 18 meters (60 feet) average, and displayed an unparalleled degree of elongation compared with modern whales. Their very small hind limbs have also been a matter of interest for paleontologists.
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Fossil finds
During the early 1800's in Louisiana and Alabama, Basilosaurus cetoides fossils were so common (and large) that they were commonly used as furniture. One vertebra was sent in to the American Philosophical Society by a Judge Bry, who was concerned that the unique finds were being destroyed by the locals. The fossils ended up in the hands of the anatomist Dr. Richard Harlan, who proclaimed it to be reptilian (and 150 feet long) and gave it the name Basilosaurus. When the British anatomist Sir Richard Owen studied the spine, mandibular fragments, arms, and ribs (recently found) he proclaimed them to be mammalian. Owen proposed renaming the find to Zeuglodon cetoides (Yoked-tooth), which is now an uncommon synonym. The name is in reference to the double rooted teeth typical of marine mammals. The species has subsequently become the state fossil of Alabama.
In 1845, "Dr." Albert Koch heard stories of giant bones in Alabama, and went down to cobble together a full skeleton. He eventually created a huge 114 foot skeleton of a "sea serpent", which he displayed in New York City, and later Europe. It was eventually shown to come from 5 different individuals, some of which were not Basilosaurus. The remains were eventually destroyed in the great Chicago fire.
Fossil finds of another species, Basilosaurus isis, have been found in the aptly named Zeuglodon valley in Egypt. The fossils were very well preserved, hind limbs included, and were rather numerous. Paleontologist Phillip 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 hussaini, have been found in Pakistan. Another fossilized species named Basiloterus drazindai was its closest known relative.
Biology
The most outstanding physical feature of Basilosaurus is its elongation. It is the most elongated cetacean known, and has been described as being the closest a whale ever came to a snake. The vertebrae are not particularly numerous, but display a far greater degree of elongation when compared with other cetaceans. Anatomical evidence suggests some flattening in the tail region, and most reconstructions show it with a very small pair of flukes. Since the flukes could not have supplied much force, it is likely the main form of locomotion was vertical undulations. A very small dorsal fin (similar to a rorqual whale’s) is usually shown, but a few reconstructions show none or perhaps a slight ridge.
The most frequently mentioned aspect of ‘‘Basilosaurus’’ is its novel hind limbs. Since they measure less than 2 feet long (on a 50-80 foot+ animal) they play no role in locomotion. When reconstructed, it appeared that the three toed limbs could only lock themselves into two positions. Because of that, it has been suggested that the hind limbs serve as a copulation "guide", much in the same manner of a boa.
Aside from those novel aspects, Basilosaurus displayed fairly regular characteristics for an Archeocete. In the early paleontology of this whale, it has been suggested that it had some form of armor plating, but that has been discounted due to misidentifications (turtle shells). The head carried no room for a "melon" organ used for echolocation present in modern day odontocetes, and the brain was comparatively smaller as well. Paleontologists have suggested that Basilosaurus and relatives were solitary and lacked the social abilities of modern cetaceans. The species are believed to have gone extinct during an ecological collapse at the end of the Eocene; but a few individuals (with no hard evidence) claim that they persist to the modern day.
See also
External links
Walking with Beasts's profile of Basilosaurus
Bejder, Lars and Hall, Brian K. Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss. Evolution and Development, 2002. Available: http://whitelab.biology.dal.ca/lb/Bejder%20and%20Hall.pdf
Sources
Zimmer, Carl. At the Water's Edge. Free Press, 1998.
Perrin, William and Wursigm Bernd, and Thweissen, J.G.M. Encyclpedia of Marine Mammals. Academic Press, 2002.
