Tylosaurus

This article is about Tylosaurus/Rhinosaurus. For the mammal, see Rhinoceros.

Tylosaurus Temporal range: Late Cretaceous
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Scleroglossa
Infraorder:	Anguimorpha
Family:	Mosasauridae
Subfamily:	Tylosaurinae
Genus:	Tylosaurus Marsh, 1872
Species
T. proriger (Cope, 1869) (type) T. nepaeolicus T. haumuriensis T. kansasensis T. capensis T. pembinensis T. saskatchewanensis

Tylosaurus (Greek τυλος/tylos "protuberance, knob" + Greek σαυρος/sauros "lizard") was a mosasaur, a large, predatory marine lizard closely related to modern monitor lizards and to snakes. Along with plesiosaurs, sharks, fish, and other genera of mosasaurs, it was a dominant predator of the Western Interior Seaway during the Late Cretaceous. Tylosaurus proriger was among the largest of all the mosasaurs (along with Hainosaurus and Mosasaurus hoffmannii), reaching maximum lengths of 15 meters or more (49+ ft). A distinguishing characteristic of Tylosaurus is its elongated, cylindrical premaxilla (snout) from which it takes its name and which may have been used to ram and stun prey and also in intraspecific combat. Stomach contents associated with specimens of Tylosaurus proriger indicate that this ferocious mosasaur had a varied diet, including fish, sharks, smaller mosasaurs, plesiosaurs, and flightless diving birds such as Hesperornis. In some paleoenvironments, Tylosaurus seems to have preferred shallow, nearshore waters (as with the Eutaw Formation and Mooreville Chalk Formation of Alabama), while favoring deeper water farther out from shore in other environments (as with the Niobrara Chalk of the western U.S.).

Discovery

Tylosaurus proriger specimen which was found with a plesiosaur in its stomach

Scales of Tylosaurus proriger (KUVP-1075)

Like many other mosasaurs, the early history of this taxon is complex and involves the infamous rivalry between two early American paleontologists, Edward Drinker Cope and Othniel Charles Marsh. Originally, the name "Macrosaurus" proriger was proposed by Cope for a fragmentary skull and thirteen vertebrae collected from near Monument Rocks in western Kansas in 1868. It was placed in the collections of the Harvard Museum of Comparative Zoology. Only a year later, Cope redescribed the same material in greater detail and referred it, instead, to the English mosasaur taxon Liodon. Then, in 1872, Marsh named a more complete specimen as a new genus, Rhinosaurus ("nose lizard"), but soon discovered that this name had already been used for a different animal. Cope suggested that Rhinosaurus be replaced by yet another new name, Rhamposaurus which also proved to be preoccupied. Marsh finally erected Tylosaurus later in 1872, to include the original Harvard material as well as additional, more complete specimens which had also been collected from Kansas. A giant specimen of T. proriger, recovered in 1911 by C. D. Bunker near Wallace, Kansas is one of the largest skeleton of Tylosaurus ever found. It is currently on display at the University of Kansas Museum of Natural history.

In 1918, Charles H. Sternberg found a Tylosaurus, with the remains of a plesiosaur in its stomach. The specimen is currently mounted in the United States National Museum (Smithsonian) and the plesiosaur remains are stored in the collections. Although these important specimens were briefly reported by C. H. Sternberg (1922), the information was lost to science until 2001. This specimen was rediscovered and described by Everhart (2004a). It is the basis for the story line in the new (2007) National Geographic IMAX movie - Sea Monsters, and a book by the same name (Everhart, 2007).

Tylosaurus proriger.

Note that the "early photograph" of a Tylosaurus skull (above) was taken by George F. Sternberg about 1926 after he collected and prepared the specimen. It was discovered in the Smoky Hill Chalk of Logan County, Kansas. Sternberg offered the specimen to the Smithsonian and included this photograph in his letter to Charles Gilmore. Copies of the original photos are in the archives of the Sternberg Museum of Natural History (FHSM). The specimen is FHSM VP-3, the exhibit specimen in the same museum.

Species

Tylosaurus skeleton.

Illustration of Tylosaurus by Charles R. Knight from 1899

Though many species of Tylosaurus have been named over the years, only a few are now recognized by scientists as taxonomically valid. They are as follows: Tylosaurus proriger (Cope, 1869), from the Santonian and lower to middle Campanian of North America (Kansas, Alabama, Nebraska, etc.); Tylosaurus nepaeolicus (Cope, 1874 ), from the Santonian of North America (Kansas); Tylosaurus haumuriensis (Hector, 1874; =Taniwhasaurus oweni), from the lower to middle Campanian of New Zealand; Tylosaurus kansasensis Everhart, 2005 , from the late Coniacian of Kansas.

A closely related genus, Hainosaurus ("Haine lizard", named after the Haine River in Belgium) is known from the Creatceous of North America and Europe. Both Tylosaurus and Hainosaurus are grouped together into the subfamily Tylosaurinae and are referred to informally as "tylosaurines" or "tylosaurs." Bell placed the tylosaurines together with the plioplatecarpine mosasaurs (Platecarpus, Plioplatecarpus, etc.) in an informal monophyletic grouping which he called the "Russellosaurinae."

T. proriger.

In popular culture

• Tylosaurus appeared in the BBC documentary Sea Monsters (revealed in the encyclopedia). It was the apex predator in what they considered "the most deadly sea ever" (the Cretaceous). It acted as the main antagonist of the story.
• In the National Geographic documentary, Sea Monsters: A Prehistoric Adventure, Tylosaurus once again is depicted as the apex predator of the Late Cretaceous seas of North America. By that time (Early Campanian, ~82 ma), mosasaurs were the largest predators living in the Earth's oceans.

File:Tylosaur MOWT.jpg

Tylosaurus exhibit at the Museum of World Treasures in Wichita, KS

• A Tylosaurus model was added to the Carnegie Collection in 2009.
• A 34 ft. long Tylosaurus found in Kansas by Alan Komrosky in 2009 is now on display at the Museum of World Treasures in Wichita, Kansas.

Further reading

Bell GL. Jr. 1997. Part IV: Mosasauridae - Introduction. pp. 281-292 In: Callaway J. M. and E. L Nicholls, (eds.), Ancient Marine Reptiles, Academic Press, 501 pages.

Everhart MJ. 2001. Revisions to the biostratigraphy of the Mosasauridae (Squamata) in the Smoky Hill Chalk Member of the Niobrara Chalk (Late Cretaceous) of Kansas. Kansas Academy of Science, Transactions 104 (1-2): 56-75.

Everhart MJ. 2002. New data on cranial measurements and body length of the mosasaur, Tylosaurus nepaeolicus (Squamata; Mosasauridae), from the Niobrara Formation of western Kansas. Kansas Academy of Science, Transactions 105 (1-2): 33-43.

Everhart MJ. 2005. Earliest record of the genus Tylosaurus (Squamata; Mosasauridae) from the Fort Hays Limestone (Lower Coniacian) of western Kansas. Transactions 108 (3/4): 149-155.

Everhart MJ. 2005. Oceans of Kansas - A Natural History of the Western Interior Sea. Indiana University Press, 322 pp.

Kiernan CR. 2002. Stratigraphic distribution and habitat segregation of mosasaurs in the Upper Cretaceous of western and central Alabama, with an historical review of Alabama mosasaur discoveries. Journal of Vertebrate Paleontology 22 (1): 91-103.

Russell DA. 1967. Systematics and morphology of American mosasaurs (Reptilia, Sauria). Yale Univ. Bull. 23: 241 pp.

Novas FE, Fernández M, Gasparini ZB, Lirio JM, Nuñez HJ, Puerta P. 2002. Lakumasaurus antarcticus, n. gen. et sp., a new mosasaur (Reptilia, Squamata) from the Upper Cretaceous of Antarctica. Ameghiniana 39 (2): 245-249.

External links

• Oceans of Kansas; includes much additional information and many illustrations and photographs of tylosaurines, including restorations and skeletons.
• E.D. Cope's original description of Macrosaurus proriger from western Kansas, with the published figure (1870) and recent photographs.