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Irritator

Say it: ih-RIT-uh-tor

Name means: “the irritator, named for the irritation paleontologists felt when they saw the fossil had been damaged”1

Ate: MeatSpinosaursEarly Cretaceous

Irritator was a meat-eating dinosaur with a long, narrow snout and a small crest on its head. It lived in what is now Brazil about 110 million years ago. It is one of the smallest spinosaurs known.1

Lived

120 to 113 million years ago3

Early Cretaceous

Fossils found in

Brazil, in the Romualdo Formation of the Araripe Basin1 3

Food

Meat1

Length

6 to 8 m1

estimated

Weight

1 tonnes1

Height

2 m1

head height from skeletal mount

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

How tall was it?

head height from skeletal mount

How heavy was it?

as heavy as 33 big dogs

as long as 8 dogs nose to tailas long as 44 bananas end to endas heavy as 200 watermelonsabout as tall as a door

How big was Irritator compared to YOU?

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cool stuff

Fun facts

Irritator's skull is the most complete skull of any spinosaurid dinosaur ever found.1

Its name comes from the irritation scientists felt because fossil collectors had damaged and altered the skull before it was studied.1

A tooth from Irritator was found stuck in the neck bone of a pterosaur, showing that it ate pterosaurs, either by hunting or scavenging.1

Irritator had a thin crest on top of its head, and strong neck muscles were probably attached there.1

Its nostrils were positioned far back on its snout, not at the tip like in many other dinosaurs.1

Irritator lived in a coastal lagoon environment that was surrounded by dry areas.1

The fossil was originally thought to be from a pterosaur, then a maniraptoran dinosaur, before being identified as a spinosaurid in 1996.1

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

?How big was Irritator?

About 6 to 8 metres (20 to 26 feet) long and weighed around 1 tonne (1.1 short tons). It was one of the smallest spinosaurids.1

?What did Irritator eat?

It ate fish and other small animals, like today's crocodiles. A tooth was found stuck in a pterosaur neck bone, so it also ate pterosaurs, either by hunting or scavenging.1

?Why is it called Irritator?

Its name comes from the word 'irritation' because scientists were annoyed that fossil collectors had damaged and altered the skull before they could study it.1

?Did Irritator have feathers?

Nobody knows for sure. No fossil feathers have been found with Irritator, and most spinosaurids are not known to have had feathers.1

?Could Irritator swim?

It may have been semiaquatic, meaning it spent time in water. It lived in a coastal lagoon and probably hunted fish, like today's crocodiles.1

?Was Irritator bigger than T. rex?

No, it was much smaller. Irritator was about 6 to 8 metres long, while T. rex could be over 12 metres long.1

?Did Irritator have a sail on its back?

One possible skeleton suggests it had a sail, like other spinosaurids, but since only a skull has been found, the sail is a guess.2

?When did Irritator live?

It lived during the Early Cretaceous Period, about 113 to 110 million years ago.1

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Myth buster

Myth: Some people think Irritator was a fully aquatic dinosaur that only ate fish.

Truth: Scientists think Irritator was a generalist eater, catching fish and other small prey, and it may have also scavenged. It probably lived both on land and in water.1

For dino experts

Scientific name: Irritator
Named by: Martill et al. 19963
Group: Spinosaurs
Family / clade: Spinosauridae3
Classification: Theropoda > Spinosauridae3
Age of the rocks: 120 to 113 million years (Aptian)3
Rock formations: Romualdo3
Countries: Brazil3
Fossil records: 1 in the Paleobiology Database3
Discovery: The skull was found by fossil dealers in Brazil and sold to a museum in Germany. It was described by Martill and colleagues in 1996, and the species was named Irritator challengeri.1 3
Still debated: Scientists are still unsure whether Irritator actively hunted pterosaurs or just ate their remains.1

Where the facts come from

Irritator (en.wikipedia.org)
Irritator | Natural History Museum (nhm.ac.uk)
Irritator 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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