Dino card No. 1153 of 2,027

Megalneusaurus

Say it: MEG-al-NEW-sore-us

Name means: “king of large swimming lizards”1

Ate: MeatPlesiosaursLate JurassicNot technically a dinosaur

Megalneusaurus was a giant marine reptile that swam in the shallow Sundance Sea during the Late Jurassic. It was one of the biggest predators in North America at that time, with four flippers and a big head.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

162 to 155 million years ago3

Late Jurassic

Fossils found in

Wyoming, USA, and possibly Alaska, USA1

Food

Meat1 2

Length

7 to 9 m1

estimated

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

as long as 2 cars parked in a rowas long as 50 bananas end to end

How big was Megalneusaurus compared to YOU?

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

cool stuff

Fun facts

Megalneusaurus was one of the largest pliosaurs in North America, measuring about 7 to 9 meters (23 to 30 feet) long.1

Its back flippers were bigger than its front flippers, which is unusual for plesiosaurs.1

Fossil stomach contents include tiny hooks from squid-like animals and bits of fish bones.1 2

It lived in the Sundance Sea, a shallow sea that covered parts of North America during the Jurassic.1

Scientists think it was an ambush predator, waiting to surprise its prey.1

A specimen from Alaska suggests it could also live in colder waters.1

AI-made picture of Megalneusaurus — An AI-made picture of how Megalneusaurus 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 Megalneusaurus

?How big was Megalneusaurus?

Megalneusaurus was about 7 to 9 meters (23 to 30 feet) long. Some estimates say it could reach around 13 meters (43 feet).1

?What did Megalneusaurus eat?

It ate squid-like animals and fish, based on hooklets and fish bones found in its stomach. It may also have eaten other plesiosaurs.1 2

?Could Megalneusaurus live in cold water?

Yes. A specimen found in Alaska shows it could live in colder waters, where there were fewer animals.1

?Was Megalneusaurus a dinosaur?

No, it was a marine reptile called a pliosaur, not a dinosaur. It lived in the sea.1

Ask Rex about Megalneusaurus

Rex only answers questions about this page. 3 questions a day.

Rex is an AI and can make mistakes. He runs on servers in the EU and questions are never saved. Never type your name or other personal things.

Myth buster

Myth: Some people think Megalneusaurus was a dinosaur.

Truth: It was a plesiosaur, a marine reptile, not a dinosaur.1

For dino experts

Scientific name: Megalneusaurus
Named by: Knight 18983
Group: Plesiosaurs
Family / clade: Plesiosauria3
Classification: Plesiosauria > Sauropterygia3
Age of the rocks: 162 to 155 million years (Oxfordian)3
Rock formations: Sundance3
Countries: USA3
Fossil records: 1 in the Paleobiology Database3
Discovery: Wilbur Clinton Knight found and described the first fossils in 1895, near Ervay, Wyoming. He first called it Cimoliosaurus rex, then gave it its own genus name in 1898.1 2
Still debated: Scientists debate whether Megalneusaurus is a valid genus because many of the original fossils were lost.1

Where the facts come from

Megalneusaurus (en.wikipedia.org)
REDISCOVERY OF WILBUR KNIGHT’S MEGALNEUSAURUS REX SITE: NEW MATERIAL FROM AN OLD PIT (wyomingdinosaurcenter.org)
Megalneusaurus 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.

Rex is hungry! Dino Wiki is a dad's project for his dino-loving son, free with no ads. Grown-ups can feed Rex a snack to help keep it online.Feed Rex