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DinosaursNamesPrehistoric Database
Early Jurassic

Plesiosaurus

Plesiosaurus dolichodeirus • "Near Lizard"

Plesiosaurus was an Early Jurassic marine reptile. It was not a dinosaur: plesiosaurs lived in the oceans and were a separate reptile group. Four flippers propelled its body through water, while its teeth suggest it caught relatively small prey.

Length
≈4.5 m
Weight
≈0.5 t
Diet
Piscivore
Danger
Battle this dinosaurView gallery
Plesiosaurus (Plesiosaurus dolichodeirus) — illustrated species reference

Overview

Plesiosaurus was an Early Jurassic marine reptile. It was not a dinosaur: plesiosaurs lived in the oceans and were a separate reptile group. Four flippers propelled its body through water, while its teeth suggest it caught relatively small prey.

“Mary Anning discovered the first nearly complete Plesiosaurus skeleton in 1823 on the Dorset coast, helping reveal the animal’s distinctive body plan.”

Key facts

Strengths

  • Adapted to its prehistoric environment

Weaknesses

  • Limited fossil evidence for detailed behavior

Natural weapons

  • Natural jaws, teeth, or defensive anatomy

Movies vs. science

Myth: Popular media often simplifies prehistoric animal behavior.

Reality: Fossils provide the strongest evidence for anatomy and ecology.

Size & simulator stats

The best-known species, Plesiosaurus dolichodeirus, was about 3.5 m long.

Length
4.5 m
Height
1.5 m
Weight
0.5 t

Illustrative simulator values (not measured biology)

Attack52/100
Defense48/100
Speed58/100
Intelligence42/100
Bite force ≈ 900 PSI

See how Plesiosaurus measures up in the sourced size comparison chart.

Habitat

Early Jurassic seas. Well-known fossils come from the Dorset coast of southern England.

Shallow seas; classic fossils come from the Dorset coast of southern England.

Diet

The skull and teeth indicate prey such as fish and crustaceans.

Carnivore, likely feeding on small fish and other marine animals. Diet is inferred from skull and teeth.

Fossils & discovery

First described from Fossil record (Multiple fossil formations).Mary Anning discovered the first nearly complete Plesiosaurus skeleton in 1823 on the Dorset coast, helping reveal the animal’s distinctive body plan.

Research sources

Sources checked on by the Dinosaurs Names Editorial Team. Editorial policy

Battle Arena

Can anything beat Plesiosaurus?

Send Plesiosaurus into an illustrative matchup against any other species and compare attack, defense, and bite force.

Fight as Plesiosaurus