Dino card No. 1451 of 2,027

Plesiosaurus

Say it: PLEE-see-oh-SORE-us

Name means: “near reptile”1

Ate: MeatPlesiosaursLate Triassic to Late CretaceousNot technically a dinosaur

Plesiosaurus was a marine reptile that swam in the oceans while dinosaurs lived on land. It had a long neck, a small head, and four flipper-like limbs to push through the water. It was about 3.5 metres long and ate small prey like fish and crustaceans.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

206 to 66 million years ago5

Late Triassic to Late Cretaceous

Fossils found in

Fossils have been found in the United Kingdom, especially along the Jurassic Coast, and also in France, the USA, Belgium, New Zealand, and South Africa.1 2

Food

Meat1 2

Length

3.5 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 4 dogs nose to tailas long as 19 bananas end to end

How big was Plesiosaurus compared to YOU?

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

cool stuff

Fun facts

Plesiosaurus was named in 1821 by William Conybeare and Henry Thomas De la Beche, and the name means 'near reptile'.1

Mary Anning discovered an almost complete Plesiosaurus skeleton in 1823, which helped scientists understand what these animals looked like.1

Plesiosaurs swam with four flipper-like limbs, and experiments with robot flippers showed they could generate 60% more thrust from their back flipper by timing both limbs carefully.1

Plesiosaurs were unable to return to land, so they likely gave birth to live young in the open water, as supported by a preserved foetus in a related species.1

Plesiosaurs survived for more than 140 million years, making it through multiple extinctions that wiped out other groups.1

Some plesiosaurs swallowed stones that stayed in their stomachs, possibly to help break up food or to help with buoyancy.1

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

?Is Plesiosaurus a dinosaur?

No, it is a marine reptile that lived in the oceans while dinosaurs lived on land. It is only distantly related to dinosaurs.1

?How big was Plesiosaurus?

It was about 3.5 metres (11 feet) long.3 1

?What did Plesiosaurus eat?

It ate small prey like fish and crustaceans.1

?When did Plesiosaurus live?

It lived during the Early Jurassic, about 203 to 174 million years ago.3

?Who discovered Plesiosaurus?

Mary Anning discovered the first complete skeleton in 1823 near Lyme Regis, England.3 1

?Did Plesiosaurus have live babies?

Yes, it gave birth to live young in the water. A fossil of a related species shows a single large baby inside its mother.1 4

?Could Plesiosaurus go on land?

No, it was fully adapted to life in the water and could not return to land.1

Ask Rex about Plesiosaurus

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Myth buster

Myth: Plesiosaurs are often thought to be dinosaurs, especially because they lived at the same time.

Truth: Plesiosaurs are marine reptiles and are only distantly related to dinosaurs, which lived on land.1

For dino experts

Scientific name: Plesiosaurus
Named by: de la Beche and Conybeare 18215
Group: Plesiosaurs
Family / clade: Plesiosauroidea5
Classification: Plesiosauria > Sauropterygia5
Age of the rocks: 206 to 66 million years (Rhaetian / Maastrichtian)5
Rock formations: Kimmeridge Clay, Charmouth Mudstone, Westbury5
Countries: United Kingdom, France, USA, Belgium, New Zealand, South Africa5
Fossil records: 55 in the Paleobiology Database5
Discovery: Plesiosaurus was named in 1821 by William Conybeare and Henry Thomas De la Beche, and Mary Anning discovered an almost complete skeleton in 1823.1
Still debated: Scientists still debate how plesiosaurs used their four flippers to swim, and whether the stones they swallowed helped with digestion or buoyancy.1

Where the facts come from

What is a plesiosaur? The prehistoric sea creatures that inspired the Loch Ness Monster | Natural History Museum (nhm.ac.uk)
PBDB Taxon (paleobiodb.org)
Plesiosaurus (Wikipedia) (Wikipedia)
Plesiosaur (en.wikipedia.org)
Plesiosaurus 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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