Dino card No. 1215 of 2,027

Mosasaurus

Say it: MOH-sah-SORE-us

Name means: “Meuse lizard, after the Meuse River in the Netherlands”1

Ate: MeatMosasaursLate Cretaceous to Cenozoic, the age of mammalsNot technically a dinosaur

Mosasaurus was a giant marine reptile that ruled the oceans at the end of the Age of Dinosaurs. It was not a dinosaur but a close relative of modern lizards and snakes. With its powerful jaws and long tail, it was a top predator in the sea.1

Fun fact: this sea reptile swam while dinosaurs walked on land. Everyone calls them dinos, but they were a different branch of reptiles.

Lived

100 to 62 million years ago5

Late Cretaceous to Cenozoic, the age of mammals

Fossils found in

Fossils have been found in many places around the world, including the Netherlands, the United States (Alabama, Colorado, New Jersey, South Dakota, Texas, and others), Canada, Morocco, Japan, New Zealand, and Antarctica.5 1

Food

Meat1

Length

10 to 17 m1

estimates vary by species; the largest species is Mosasaurus hoffmannii

Weight

10 tonnes1

estimate for adult Mosasaurus

When did it live?

Before the dinosaurs

Age of dinosaurs

Age of mammals

400 million years ago25266today

How big was it?

How long was it?

How heavy was it?

as heavy as 7 cars

as long as 4 cars parked in a rowas long as 94 bananas end to endas heavy as 1.5 elephantsas heavy as 2000 watermelons

How big was Mosasaurus compared to YOU?

Just maths in your browser. Nothing is saved or sent anywhere.

cool stuff

Fun facts

Mosasaurus was first discovered in 1766 in a limestone quarry near Maastricht, Netherlands, long before the word 'dinosaur' was even invented.1

The first Mosasaurus skull was seized by the French army in 1795 and is still on display in Paris today.1

Mosasaurus had a special joint in its lower jaw that allowed it to open its mouth extra wide, so it could swallow very large prey.1

Unlike most lizards, Mosasaurus gave birth to live young in the open ocean and did not need to come ashore to lay eggs.1

Some Mosasaurus species were warm-blooded, which helped them live in both cold polar waters and warm tropical seas.1

Mosasaurus teeth were curved and sharp, and they sat in sockets like ours, which helped it bite hard without hurting itself.1

Mosasaurus lived during the Late Cretaceous Period, from about 94 million to 66 million years ago, when a huge sea called the Western Interior Seaway covered parts of North America.1

AI-made picture of Mosasaurus — An AI-made picture of how Mosasaurus might have looked, made by a computer from what scientists know. It is a guess: the real animal may have looked different, and nobody knows its true colours.

you asked

Most asked questions about Mosasaurus

?Was Mosasaurus a dinosaur?

No, Mosasaurus was not a dinosaur. It was a giant marine reptile and a close relative of modern lizards and snakes.1 2

?How big was Mosasaurus?

The largest species, Mosasaurus hoffmanni, may have reached 17 to 18 metres (56 to 59 ft), though many scientists think 11 to 12 metres (36 to 39 ft) is more likely. Other species were about 8 to 10 metres (26 to 33 ft) long.1 2

?What did Mosasaurus eat?

Mosasaurus was a carnivore that ate fish, sharks, squid, birds, sea turtles, and even other mosasaurs. It could swallow very large prey thanks to a special hinge in its jaw.1 3 2

?When did Mosasaurus live?

Mosasaurus lived during the Late Cretaceous Period, from about 82 to 66 million years ago, when it went extinct along with the dinosaurs.2

?Could Mosasaurus swim fast?

Mosasaurus was a good swimmer that used side-to-side tail movements to move through water, but it probably could not swim very fast for long periods.3 4

?Did Mosasaurus have any predators?

Adult Mosasaurus had no natural predators, but young ones were hunted by sharks and giant fish. Mosasaurs also fought and sometimes ate each other.3 2

?Where have Mosasaurus fossils been found?

Mosasaurus fossils have been found in North and South America, Europe, Africa, Western Asia, and Antarctica, showing it lived in oceans all over the world.2

?Was Mosasaurus bigger than T. rex?

Yes, Mosasaurus was longer than T. rex. The largest Mosasaurus species could reach 17 to 18 metres (56 to 59 ft) long, while T. rex was about 12 metres (40 ft) long.1 2

?Did Mosasaurus lay eggs?

No, Mosasaurus gave birth to live young in the open ocean. Scientists found a fossil of a pregnant mosasaur with five babies inside.1 3

?How did Mosasaurus become extinct?

Mosasaurus went extinct about 66 million years ago, at the same time as the dinosaurs, likely because of the asteroid impact that caused a mass extinction.2

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Myth buster

Myth: Mosasaurus is a dinosaur.

Truth: Mosasaurus is not a dinosaur. It is a marine reptile and a member of the squamate group, which includes modern lizards and snakes.1

For dino experts

Scientific name: Mosasaurus
Named by: Parkinson 18225
Group: Mosasaurs
Family / clade: Mosasauridae5
Classification: Mosasauroidea5
Age of the rocks: 100 to 62 million years (Cenomanian / Danian)5
Rock formations: Navesink, Severn, Pierre Shale5
Countries: USA, Syria, United Kingdom, Morocco, New Zealand, Poland5
Fossil records: 130 in the Paleobiology Database5
Discovery: The first Mosasaurus fossils were found in 1766 near Maastricht, Netherlands. The animal was named Mosasaurus in 1822 by James Parkinson, after the Meuse River. The famous French naturalist Georges Cuvier later confirmed it was a giant lizard.5 1
Still debated: Scientists are still debating the exact sizes of different Mosasaurus species, because only a few complete skeletons have been found.1

Where the facts come from

What is a mosasaur? Facts about Mosasaurus and its relatives | Natural History Museum (nhm.ac.uk)
Mosasaurus (Wikipedia) (Wikipedia)
Mosasaur: Apex Predator of the Western Interior Seaway (U.S. National Park Service) (nps.gov)
Russian Geological Research Institute (karpinskyinstitute.ru)
Mosasaurus in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

Every fact on this page has a number that points to its source. If we got something wrong, sorry, we are dino fans, not a science journal. Tell us at [email protected] and we will fix it.

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