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Tricleidus

Say it: try-KLEE-dus

Name means: “three keyed (or three locked) lizard”1

Ate: MeatPlesiosaursEarly Jurassic to Late JurassicNot technically a dinosaur

Tricleidus was a plesiosaur, a marine reptile that swam in the seas during the Jurassic Period. It had a small head, a long neck, and flippers to paddle through the water. It was not a dinosaur, but a distant cousin that lived in the ocean.1 3

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

Lived

184 to 155 million years ago3

Early Jurassic to Late Jurassic

Fossils found in

Fossils have been found in the United Kingdom and Norway.3 1

Food

Meat3

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

cool stuff

Fun facts

Tricleidus is known from only one skeleton, found in the Oxford Clay of England.1

The first fossil was a shoulder girdle, which is part of the skeleton that supports the flippers.2

It lived about 165 to 161 million years ago, during the Callovian age of the Jurassic.2

One species that was once called Tricleidus svalbardensis was moved to another genus, Colymbosaurus, in 2012.1

Tricleidus belongs to a group called Cryptoclididae, which were plesiosaurs with long necks and small heads.1 3

The type specimen is stored in a museum and is called BMNH R3539.1 2

AI-made picture of Tricleidus — An AI-made picture of how Tricleidus 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.

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Myth buster

Myth: Some people think Tricleidus was a dinosaur because it lived long ago and is often shown in dinosaur books.

Truth: Tricleidus was a plesiosaur, a marine reptile, not a dinosaur. Dinosaurs lived on land and had different body features.1

For dino experts

Scientific name: Tricleidus
Named by: Andrews 19093
Group: Plesiosaurs
Family / clade: Cryptoclididae3
Classification: Plesiosauria > Sauropterygia3
Age of the rocks: 184 to 155 million years (Toarcian / Oxfordian)3
Rock formations: Oxford Clay3
Countries: United Kingdom, Norway3
Fossil records: 3 in the Paleobiology Database3
Discovery: Tricleidus was named by C. W. Andrews in 1909, based on a skeleton found in the Oxford Clay of Peterborough, England. The type species is Tricleidus seeleyi.1 3
Still debated: Scientists are still debating how Tricleidus is related to other plesiosaurs, and some fossils from Norway were once assigned to it but later moved to another genus.1

Where the facts come from

Tricleidus (en.wikipedia.org)
PBDB Taxon (paleobiodb.org)
Tricleidus 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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