Dino card No. 1549 of 2,027

Rhomaleosaurus

Say it: ro-MAL-ee-oh-SORE-us

Name means: “strong lizard”1

Ate: MeatPlesiosaursEarly JurassicNot technically a dinosaur

Rhomaleosaurus was a giant marine reptile that swam in the seas during the Early Jurassic period, about 183 to 175 million years ago. It was one of the biggest predators in the ocean at that time, with a huge head and a long neck, and it ate other sea creatures like ichthyosaurs and ammonites.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

201 to 175 million years ago5

Early Jurassic

Fossils found in

Northamptonshire and Yorkshire, United Kingdom1

Food

Meat1 5

Length

7 m1 2

estimate for the holotype specimen

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

as long as 7 dogs nose to tailas long as 39 bananas end to end

How big was Rhomaleosaurus compared to YOU?

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

cool stuff

Fun facts

Rhomaleosaurus had a very long neck compared to other pliosaurs, but still had a gigantic head, making it a mix of features from both long-necked and short-necked plesiosaurs.2

The first fossil of Rhomaleosaurus was found in 1848 in an alum quarry at Kettleness, near Whitby, England, and was kept at Mulgrave Castle for five years before being sent to Dublin.1

The skull of the holotype specimen is 88 centimeters long, and the whole animal was about 7 meters (23 feet) long.2

Rhomaleosaurus lived at the same time as the large ichthyosaur Temnodontosaurus, and both were top predators in the same ocean.1

Scientists think Rhomaleosaurus could pick up scents while underwater, helping it find prey.1

The name Rhomaleosaurus was given by Harry Seeley in 1874, based on a fossil that was originally thought to be a species of Plesiosaurus.1 5

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

?How big was Rhomaleosaurus?

About 7 metres (23 feet) long.1 3

?What did Rhomaleosaurus eat?

It ate ichthyosaurs, ammonites, other plesiosaurs, belemnites, and fish.1 4

?Was Rhomaleosaurus a dinosaur?

No, it was a marine reptile called a plesiosaur, not a dinosaur.1 4

?When did Rhomaleosaurus live?

It lived during the Early Jurassic period, about 183 to 175 million years ago.1

?Where was Rhomaleosaurus found?

Fossils have been found in Northamptonshire and Yorkshire, England, in the Whitby Mudstone Formation.1 4

Ask Rex about Rhomaleosaurus

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.

For dino experts

Scientific name: Rhomaleosaurus
Named by: Seeley 18745
Group: Plesiosaurs
Family / clade: Rhomaleosauridae5
Classification: Plesiosauria > Sauropterygia5
Age of the rocks: 201 to 175 million years (Hettangian / Toarcian)5
Rock formations: Whitby Mudstone, Alum Shale, Blue Lias5
Countries: United Kingdom5
Fossil records: 15 in the Paleobiology Database5
Discovery: The first Rhomaleosaurus fossil was discovered in 1848 in an alum quarry at Kettleness, near Whitby, England. It was named Plesiosaurus cramptoni by Alexander Carte and W. H. Bailey in 1863, and later Harry Seeley placed it in its own genus, Rhomaleosaurus, in 1874.1
Still debated: Scientists still debate which species belong to Rhomaleosaurus. Some species once placed here, like Rhomaleosaurus megacephalus, are now thought to belong to other genera.1

Where the facts come from

Rhomaleosaurus (en.wikipedia.org)
The skull of the giant predatory pliosaur Rhomaleosaurus cramptoni: implications for plesiosaur phylogenetics (plesiosauria.com)
Rhomaleosaurus – Plesiosaur Directory (plesiosauria.com)
An exceptional fossil plesiosaur - Rhomaleosaurus cramptoni | National Museum of Ireland (museum.ie)
Rhomaleosaurus 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