Category: Dinosaur

Tylosaurus (Tie-lo-sore-us), Knob lizard, lived in Western interior Seaway of North America in the Late Cretaceous. There are at least three species of tylosaurs. Tylosaurs were large-bodied marine lizards armed with sturdy, conical teeth with elongated jaws. Tylosaurus reached lengths of 9-15+ meters. Hainosaurus, a large tylosaur, may be a subspecies of Tylosaurus.



Genera and Species

Classification: Anguimorpha, ‬Mosasauridae, ‬Tylosaurinae

Species: T. ‬prioriger‬, ‬T. ‬capensis, ‬T. ‬kansasensis, ‬K. ‬nepaeolicus, ‬K. ‬pembinensis, ‬K. ‬saskatchewaensis

Synonyms: Hainosaurus, Macrosaurus prioger, Rhamposaurus, Rhinosaurus,Taniwhasaurus


Tylosaurus was named for its long cylindrical snout. It could have been used to ram prey or for contests with other tylosaurs or to locate prey. It may have had a tail fluke similar to the tail ‬fin of a shark. It had huge jaws; sharp, cone-like teeth on the side of the jaw and two extra rows of teeth on the roof of its mouth. The flipper-like hands and feet meant they could not return to land even to lay eggs (Dixon, 2006).


LENGTH: 6 – 12 m (20 – 40 ft).

WEIGHT: 7 tons.


It preyed on practically everything as an apex predator. The diet was heavy on fish, but seabirds, sharks, plesiosaurs, turtles and other mosasaurs were included. They even scavenged dinosaur carcasses. They were not among the fastest swimming or the strongest mosasaurids, but they were versatile top predators.

History of Discovery

Discovery, Cope but named by Marsh ‬- ‬1872. Most fossils are found in the interior seaway but they are known other areas of North America.


Found in Niobara sea; a large inland sea that existed in North America during the mid- to late Cretaceous period filled with abundant marine life. It lived alongside several other species of mosasaurs, including the familiar Platecarpus and Plioplatecarpus.


  1. Knol, R. (2010, May 25). The Tylosaurs. Retrieved May 22, 2014, from http://www.dinosaurcollectorsitea.com/cret_sea_tylosaur.html
  2. Dixon, D. (2006). The Complete Book of Dinosaurs (pp. 10-12). London UK: Hermes House.
  3. Plesiosaurus. (2009, May 19). Tylosaurus.
  4. Tylosaurus. (n.d.). Retrieved May 22, 2014, from http://www.prehistoric-wildlife.com/species/t/tylosaurus.html