Styxosaurus
Encyclopedia
Styxosaurus is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...

 of the family Elasmosauridae
Elasmosauridae
Elasmosauridae was the family of plesiosaurs. They had the longest necks of the plesiosaurs and survived from the Late Triassic to the end of the Cretaceous. They had a diet of fish and shelless cephalopods.-Size:...

. Styxosaurus lived during the Santonian
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series. It spans the time between 85.8 ± 0.7 mya and 83.5 ± 0.7 mya...

 and Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...

 age
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...

 of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 period.

Etymology

Styxosaurus is named for the mythological River Styx (Στυξ), which separated the Greek underworld
Hades
Hades , Hadēs, originally , Haidēs or , Aidēs , meaning "the unseen") was the ancient Greek god of the underworld. The genitive , Haidou, was an elision to denote locality: "[the house/dominion] of Hades". Eventually, the nominative came to designate the abode of the dead.In Greek mythology, Hades...

 from the world of the living. The -saurus part comes from the Greek sauros (σαυρος), meaning "lizard" or "reptile."

The type specimen was found on Hell Creek in Logan County, Kansas
Logan County, Kansas
Logan County is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 2,756...

 and is the source of the genus name coined by Samuel Paul Welles
Samuel Paul Welles
Samuel Paul Welles was an American palaeontologist, who was Research Associate at the Museum of Palaeontology, University of California, Berkeley. He took part in excavations at the 'Placerias Quarry' in 1930 and the Shonisaurus discoveries of 1954 and later, in what is now the Berlin-Ichthyosaur...

, who described the genus, in 1943.

Description

The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 specimen of Styxosaurus snowii was described by S.W. Williston from a complete skull and 20 vertebrae.
Another more complete specimen - SDSMT 451 (about 36 feet (11 m) long) was discovered near Iona, South Dakota
Iona, South Dakota
Iona is an unincorporated community in Lyman County, South Dakota, United States. Although not tracked by the Census Bureau, Iona has been assigned the ZIP code of 57542....

 in 1945. The specimen was originally described and named Alzadasaurus pembertoni by Welles and Bump (1949) and remained so until it was synonimized with S. snowii by Carpenter. Its chest cavity contained about 250 gastroliths, or "stomach stones". Although it is mounted at the School of Mines as if its head were looking up and out of the water, such a position would be physically impossible .

While most predators do not use gastroliths for grinding of food, almost all reasonably complete elasmosaur specimens include gastroliths. Although it is possible Styxosaurus may have used the stones as ballast
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...

, a Styxosaurus specimen found in the Pierre Shale of western Kansas included ground up fish bones mixed with the gastroliths . In addition, the weight of the gastroliths found in elasmosaurs specimens is always much less than 1% of the estimated weight of the living animal .

While crocodiles and some other animals may use gastroliths for ballast today, it appears likely that elasmosaurs used them as a gastric mill. See Henderson (2006) contra Wings (2004).

Classification

Styxosaurus snowii is from a group called elasmosaurs
Elasmosauridae
Elasmosauridae was the family of plesiosaurs. They had the longest necks of the plesiosaurs and survived from the Late Triassic to the end of the Cretaceous. They had a diet of fish and shelless cephalopods.-Size:...

, and is closely related to Elasmosaurus platyurus
Elasmosaurus
Elasmosaurus + σαυρος sauros 'lizard') is a genus of plesiosaur with an extremely long neck that lived in the Late Cretaceous period , 80.5 million years ago.-Description:...

, which was found in Kansas
Kansas
Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...

 in 1867.

The first Styxosaurus to be described was initially called Cimoliasaurus snowii by S.W. Williston in 1890. The specimen included a complete skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

 and more than 20 cervical vertebrae
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...

 ( KUVP 1301) that were found near Hell Creek in western Kansas by Judge E.P. West.

The name was later changed to Elasmosaurus snowii by Williston in 1906 and then to Styxosaurus snowii by Welles in 1943.

A second species, Styxosaurus browni, was named by Welles in 1952. However, this has since been found to be a synonym of Hydralmosaurus serpentinus.

Description

Styxosaurus was a large plesiosaur, one of several species of a group collectively called elasmosaurs that appeared in the Late Cretaceous. Elasmosaurs typically have a neck that is at least half the length of the body, and composed of 60-72 vertebrae. The type specimen is Elasmosaurus platyurus Cope 1868.

Styxosaurus was around 11 meters (36 ft) to 12 meters (40 ft) long, with about half of the length being neck. Its sharp teeth were conical
Cone (geometry)
A cone is an n-dimensional geometric shape that tapers smoothly from a base to a point called the apex or vertex. Formally, it is the solid figure formed by the locus of all straight line segments that join the apex to the base...

 and were designed to puncture and hold rather than to cut, for, like other plesiosaurs, Styxosaurus swallowed
Swallowing
Swallowing, known scientifically as deglutition, is the process in the human or animal body that makes something pass from the mouth, to the pharynx, and into the esophagus, while shutting the epiglottis. If this fails and the object goes through the trachea, then choking or pulmonary aspiration...

 its food whole.

Diet

Styxosaurus, like most other plesiosaurs, probably fed on belemnites, fish (Gillicus, etc.) and squid. With its interlocking teeth, Styxosaurus could grab on to its slippery prey before swallowing it.

In popular culture

  • In the National Geographic 3-D film
    3-D film
    A 3-D film or S3D film is a motion picture that enhances the illusion of depth perception...

    , Sea Monsters: A Prehistoric Adventure
    Sea Monsters: A Prehistoric Adventure
    Sea Monsters: A Prehistoric Adventure is a film by National Geographic which is set in the Earth's prehistoric past. The film features state-of-the-art three dimensional photographic and computer generated characters/animals. The setting alternates between prehistory and modern day times in which...

    , Styxosaurus appeared alongside a cast of other "sea monsters", but wasn't featured in the game adaptation of the film.

Further reading

  • Everhart, M. J. 2000. Gastroliths associated with plesiosaur remains in the Sharon Springs Member of the Pierre Shale (Late Cretaceous), western Kansas. Kansas Academy of Science, Transactions 103(1-2): 58-69.
  • Cicimurri, D. J. and M. J. Everhart, 2001. An elasmosaur with stomach contents and gastroliths from the Pierre Shale (late Cretaceous) of Kansas. Kansas Acad. Sci. Trans 104(3-4):129-143.
  • Everhart, M. J. 2005a. Oceans of Kansas - A Natural History of the Western Interior Sea. Indiana University Press, 320 pp.
  • Everhart, M. J. 2005b. Elasmosaurid remains from the Pierre Shale (Upper Cretaceous) of western Kansas. Possible missing elements of the type specimen of Elasmosaurus platyurus Cope 1868? PalArch 4(3): 19-32.
  • Everhart, M. J. 2006. The occurrence of elasmosaurids (Reptilia: Plesiosauria) in the Niobrara Chalk of Western Kansas. Paludicola 5(4):170-183.
  • Henderson, J. 2006. Floating point: a computational study of buoyancy, equilibrium, and gastroliths in plesiosaurs. Lethaia 39: 227-244.
  • Welles, S. P. 1943. Elasmosaurid plesiosaurs with a description of the new material from California and Colorado. University of California Memoirs 13:125-254. figs.1-37., pls.12-29.
  • Welles, S. P. 1952. A review of the North American Cretaceous elasmosaurs. University of California Publications in Geological Sciences 29:46-144. figs. 1-25.
  • Welles, S. P. 1962. A new species of elasmosaur from the Aptian of Columbia and a review of the Cretaceous plesiosaurs. University of California Press, Berkeley and Los Angeles.
  • Welles, S. P. and Bump, J. 1949. Alzadasaurus pembertoni, a new elasmosaur from the Upper Cretaceous of South Dakota. Journal of Paleontology 23(5): 521-535.
  • Williston, S. W. 1890a. Structure of the plesiosaurian skull. Science 16(407):290.
  • Williston, S. W. 1890b. A new plesiosaur from the Niobrara Cretaceous of Kansas. Kansas Academy Science, Transactions 7:174-178, with 2 fig.
  • Williston, S. W. 1893. An interesting food habit of the plesiosaurs. Kansas Academy of Science, Transactions 13:121-122, 1 plate.
  • Williston, S. W. 1906. North American Plesiosaurs: Elasmosaurus, Cimoliasaurus, and Polycotylus. American Journal of Science 4(21):221-236.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK