Dino card No. 0574 of 2,027

Elasmosaurus

Say it: ee-LAZ-mo-SORE-us

Name means: “thin-plate reptile”1

Ate: MeatPlesiosaursLate CretaceousNot technically a dinosaur

Elasmosaurus was a giant marine reptile with an incredibly long neck, longer than a school bus! It swam in the ancient sea that once covered the middle of North America, using its four flippers to paddle through the water.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

94 to 72 million years ago4

Late Cretaceous

Fossils found in

Kansas and Wyoming, USA, and Hokkaido, Japan4 1

Food

Meat1

Length

10.3 m1

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

as long as 2.5 cars parked in a rowas long as 57 bananas end to end

How big was Elasmosaurus compared to YOU?

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

cool stuff

Fun facts

Elasmosaurus had 72 bones in its neck, which was about 7.1 meters (23 feet) long, making it one of the longest-necked animals ever.1

The first Elasmosaurus fossil was found in 1867 near Fort Wallace, Kansas, by a military doctor named Theophilus Turner.1

The scientist who named Elasmosaurus, Edward Drinker Cope, made a famous mistake: he put the skull on the tail end of the skeleton!1

Elasmosaurus lived about 80.6 to 77 million years ago, during the Late Cretaceous Period, in a shallow sea called the Western Interior Seaway.1

Despite its long neck, Elasmosaurus could not lift its head high above the water like a swan; its neck was not very flexible.1

Elasmosaurus may have used stomach stones, called gastroliths, to help grind up food in its belly.1

The name Elasmosaurus means 'thin-plate reptile', referring to the flat bones in its chest and hips.1

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

?How big was Elasmosaurus?

Elasmosaurus was about 10.3 meters (34 feet) long, with its neck alone around 7.1 meters (23 feet). That is longer than a school bus.1

?What did Elasmosaurus eat?

Elasmosaurus probably ate small fish and marine invertebrates, seizing them with its long teeth. It may have used stomach stones to help digest its food.1 2

?Was Elasmosaurus a dinosaur?

No, Elasmosaurus was a plesiosaur, a marine reptile that lived in the sea. It was not a dinosaur, though it lived during the time of dinosaurs.1 3

?Could Elasmosaurus lift its neck out of water?

No, Elasmosaurus could not raise its head and neck high above the water like a swan. Its neck was too heavy and not flexible enough, so it could only lift its head above water in very shallow water.1

?How many neck bones did Elasmosaurus have?

Elasmosaurus had 72 neck vertebrae, which is the second largest number known in any animal. Its relative Albertonectes had even more, with at least 75.1

?Where did Elasmosaurus live?

Elasmosaurus lived in the Western Interior Seaway, a shallow sea that covered the middle of North America about 80.6 to 77 million years ago. Its fossils have been found in Kansas, USA.1

?Why did Elasmosaurus have such a long neck?

Scientists are not sure why Elasmosaurus had such a long neck. It may have helped in feeding, perhaps by sneaking up on prey, but the exact reason is unknown.1 2

?What was Cope's mistake with Elasmosaurus?

Edward Drinker Cope, who named Elasmosaurus, mistakenly put the skull on the tail end of the skeleton in his reconstruction. This famous error was pointed out by his rival Othniel Charles Marsh.1

Ask Rex about Elasmosaurus

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Myth buster

Myth: Many people think Elasmosaurus could hold its neck high out of the water like a giraffe.

Truth: Scientists now know its neck was not flexible enough to lift high; it probably kept its neck low in the water while swimming.1

For dino experts

Scientific name: Elasmosaurus
Named by: Cope 18684
Group: Plesiosaurs
Family / clade: Elasmosauridae4
Classification: Plesiosauria > Elasmosauridae > Sauropterygia4
Age of the rocks: 94 to 72 million years (Turonian / Campanian)4
Rock formations: Pierre Shale4
Countries: Japan, USA4
Fossil records: 9 in the Paleobiology Database4
Discovery: Elasmosaurus was named in 1868 by American paleontologist Edward Drinker Cope, based on a partial skeleton found in Kansas. The fossil was dug out of shale and shipped to Philadelphia in crates.1
Still debated: Scientists are still not sure exactly what Elasmosaurus used its extremely long neck for, though it may have helped it catch prey on the seafloor or surprise fish.1

Where the facts come from

Elasmosaurus (en.wikipedia.org)
BBC - Science & Nature - Sea Monsters - Fact File: Elasmosaurus (bbc.co.uk)
Fossil Focus: Elasmosaurs – PALAEONTOLOGY[online] (palaeontologyonline.com)
Elasmosaurus 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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