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 skeletons 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 on display in the Smithsonian, while the plesiosaur remains are stored in the collections.
Although these important specimens were briefly reported by Sternberg in 1922 the find was largely overlooked until 2001.
This specimen was rediscovered and described by Michael J. Everhart in 2004.
This find formed the basis for the story line in the 2007 National Geographic IMAX movie  Sea Monsters: A Prehistoric Adventure, and a book Sea Monsters: Prehistoric Creatures of the Deep.

A photograph of a Tylosaurus skull 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 a 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.

A 34 feet (10 m) long Tylosaurus found in Kansas by Alan Komrosky in 2009 is now on display at the Museum of World Treasures in Wichita, Kansas.

Tylosaurus has now been described from formations in Saskatchewan and South Dakota.
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 skeletons 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 on display in the Smithsonian, while the plesiosaur remains are stored in the collections. Although these important specimens were briefly reported by Sternberg in 1922 the find was largely overlooked until 2001. This specimen was rediscovered and described by Michael J. Everhart in 2004. This find formed the basis for the story line in the 2007 National Geographic IMAX movie  Sea Monsters: A Prehistoric Adventure, and a book Sea Monsters: Prehistoric Creatures of the Deep.
A photograph of a Tylosaurus skull 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 a 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.
A 34 feet (10 m) long Tylosaurus found in Kansas by Alan Komrosky in 2009 is now on display at the Museum of World Treasures in Wichita, Kansas.
Tylosaurus has now been described from formations in Saskatchewan and South Dakota.
Tylosaurus