1. Education
You can opt-out at any time. Please refer to our privacy policy for contact information.



Mosasaurus skull - CMRNWR Phillips County Montana - Museum of the Rockies - 2013-07-08
23165290@N00/Flickr/CC BY-SA 2.0


Mosasaurus (Greek for "Meuse lizard"); pronounced MOE-za-SORE-us



Historical Period:

Late Cretaceous (70-65 million years ago)

Size and Weight:

About 50 feet long and 15 tons


Fish, squids, and shellfish

Distinguishing Characteristics:

Enormous size; blunt, alligator-like head; fin on end of tail


About Mosasaurus:

The remains of Mosasaurus were discovered well before educated society knew anything about evolution, dinosaurs, or marine reptiles--in a mine in Holland in the late 18th century (hence this creature's name, after the nearby Meuse river). The unearthing of these fossils led early naturalists like Georges Cuvier to speculate, for the first time, about the possibility that currently extinct species had once lived on earth, which flew in the face of accepted religious dogma of the time.

The fearsome Mosasaurus was a giant member of the family of marine reptiles known as mosasaurs, which were characterized by their big heads, powerful jaws, streamlined bodies and front and rear flippers. Mosasaurs were only distantly related to the pliosaurs and plesiosaurs that preceded them (and which they largely supplanted from dominance of the world's oceans during the late Cretaceous period); today, evolutionary biologists believe they were most closely related to modern-day snakes and monitor lizards.


©2014 About.com. All rights reserved.