Basilosaurus

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Placentalia
Superordo: Cetartiodactyla
Ordo: Cetacea
Subordo: †Archaeoceti
Familia: Basilosauridae
Genus: Basilosaurus
Species: B. cetoides - B. drazindai - B. isis

Vernacular Names
Internationalization
日本語: バシロサウルス
中文: 龍王鯨

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Basilosaurus ("King Lizard") is a genus of cetacean that lived from 40 to 34 million years ago in the Late Eocene.[1] Its fossilized remains were first discovered in the southern United States (Louisiana), and were initially believed to be some sort of reptilian sea monster, hence the suffix -"saurus", but later it was found that was not the case.[2] 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 meters (60 ft) in length, and is believed to have been the largest animal to have lived in its time.[3] 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 is the state fossil of Mississippi and Alabama in the United States.

Fossil finds
A skull of Basilosaurus cetoides
Size of Basilosaurus, compared to a human.

During the early 19th century in the American South, Basilosaurus cetoides fossils were so common (as well as large) that they were regularly used as furniture. 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”.[4]

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.
Albert Koch's "Hydrarchos" fossil skeleton from 1845.

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 (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 5 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 today in the National Museum of Natural History, the only real specimen currently exhibited in the world.[5] There is a plaster cast on display in the Alabama Museum of Natural History.

Fossil finds of another 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 named Basiloterus husseini was its closest known relative, but was not as large or elongated.

Biology
Reconstruction of Basilosaurus.

Basilosaurus was highly elongated. It accomplished this through an unparalleled elongation of its vertebrae, and has been described as being the closest a whale ever came to a snake. It is also believed to have had unusual locomotion, compared with all other cetaceans; similarly sized thoracic, lumbar, sacral and caudal vertebrae imply that Basilosaurus moved in an anguilliform (eel-like) fashion, only vertically. Even more oddly, paleontologist Philip Gingerich theorized that it may also have moved in a horizontal anguilliform fashion to some degree, something completely unknown in modern cetaceans. The skeletal anatomy of the tail suggests that a small fluke was probably present, which would have only aided vertical motion. Most reconstructions show a small, speculative dorsal fin similar to a rorqual whale’s, but other reconstructions show a dorsal ridge.
Artist's conception of a pair of Basilosaurus

The whale also possessed small, 0.6 meter (2 ft) hind limbs, which clearly cannot aid locomotion on a 15-25 meter (50-85 foot) animal. Analysis has shown that the reduced limbs could only snap between two positions. They appear similar to the reduced legs used as copulatory guides on boas, and might have been used in the same manner.

The vertebrae of the whale appear to have been hollow, and it is likely that they were fluid filled as well. This would imply that Basilosaurus typically only functioned in two dimensions at the sea's surface, compared with the three dimensional habit 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 were 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.

At one point of time it was believed that Basilosaurus had some sort of armor plating, but it was likely the misidentification of turtle shells.

In popular culture

Herman Melville recounts the discovery of the Alabama Basilosaurus and the subsequent discovery that it was a marine cetacean in chapters 104-105 of Moby-Dick (1851).

Basilosaurus was featured in the second episode of BBC's Walking with Beasts (2001). It featured the breeding cycle of Basilosaurus. First, the featured Basilosaurus mated, after which food ran out in her territory, and she journeyed into a saltwater lagoon. In one instance, she was unsuccessful in hunting a Moeritherium. In the end, the Basilosaurus dines on baby Dorudon and is shown with her offspring one year later. In a follow-up to Walking with Beasts called Sea Monsters (2003), the Basilosaurus is the top hazard in the episode “Fourth Most Dangerous Sea of All Time”. It was shown as being more aggressive and territorial than in Walking with Beasts.

D&D accessory Frostburn (2004) has a Zeuglodon (a.k.a. Basilosaurus) monster entry.


References

1. ^ "Basilosaurus". The Paleobiology Database. http://paleodb.org/cgi-bin/bridge.pl?action=checkTaxonInfo&taxon_no=36681&is_real_user=1. Retrieved 2009-05-25.
2. ^ "Basilosaurus fact file". BBC — Science & Nature. http://www.bbc.co.uk/science/seamonsters/factfiles/basilosaurus.shtml. Retrieved 2009-05-25.
3. ^ Basilosaurus
4. ^ Switek, Brian (September 21, 2008) "The Legacy of the Basilosaurus" Laelaps
5. ^ "Basilosaurus page at the Smithsonian". http://www.mnh.si.edu/onehundredyears/featured_objects/Basilosaurus.html. Retrieved 2010-12-08.

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