Mosasaurus Fact Sheet

Common Name:

Mosasaurus hoffmannii

Scientific Name:

Hoffmann's Meuse River lizard

Wild Status:

Cretaceous Period, 70-66 MYA







Life Span:



56 feet long, 8 tons

Cool Facts:

  • Even though it is a reptile, Mosasaurus has a few characteristics that are decidedly non-reptilian. For starters, it gave birth to live young. Being so adapted for aquatic life, females were unable to come ashore to lay eggs like sea turtles do.
  • Young would have been born tail-first to prevent drowning. Analysis of its bones indicates that Mosasaurus would have been able to keep its body temperature fixed several degrees above that of the surrounding sea water, meaning it was warm-blooded. All these seemingly mammalian traits are all adaptations to being a marine reptile.


Although it lived at the same time, Mosasaurus was not a dinosaur - it was not even a close relative. Mosasaurs were actually a variety of lizard that had adapted for an oceanic lifestyle. Their legs evolved into flippers and their tails flattened to make swimming more efficient. Modern monitor lizards, such as the infamous Komodo dragon, are the closest living relatives of the Mosasaurus. When first discovered, it was believed that Mosasaurus swam by undulating its elongated body in a manner similar to a snake or eel. This is an excellent design for efficient long-distance swimming and pursuit predation. However, recent discoveries have shown that Mosasaurus actually possessed crescent-shaped tail flukes not unlike those of sharks. Rather than moving the entire body side to side, Mosasaurus would have only used their tails for locomotion. With body held stiff to reduce water resistance, Mosasaurus would have been able to swim with considerable speed and more and may have relied more on ambush to capture prey.

Taxonomic Breakdown:

Kingdom - Animalia Phylum - Chordata Class - Reptilia Order - Squamata Family - Mosasauridae Genus - Mosasaurus Species - M. hoffmannii

Conservation & Helping:

Mosasaurus is currently extinct and lived from 70 to 66 million years ago.

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