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Chasmosaurus

Say it: KAZ-mo-SORE-us

Name means: “opening lizard, referring to the large openings in its frill”1

Ate: PlantsHorned dinosLate Cretaceous

Chasmosaurus was a plant-eating dinosaur with a huge bony frill on its head. It lived in what is now Canada and the USA during the Late Cretaceous period, about 77 to 74 million years ago. It was smaller than its famous relative Triceratops, but still weighed as much as a car.1

Lived

84 to 72 million years ago3

Late Cretaceous

Fossils found in

Alberta, Canada and Montana, USA1 3

Food

Plants3

Length

4.3 to 4.8 m1

Weight

1.5 tonnes to 2 tonnes1

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

How long was it?

How heavy was it?

as heavy as 1.5 cars

as long as 5 dogs nose to tailas long as 27 bananas end to endas heavy as 67 big dogsas heavy as 400 watermelons

How big was Chasmosaurus compared to YOU?

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cool stuff

Fun facts

The name Chasmosaurus means 'opening lizard' because its frill had huge holes, called fenestrae, that made it lighter.1

It was first named Protorosaurus, but that name was already used for another reptile, so it was changed to Chasmosaurus in 1914.1

Some scientists think that Chasmosaurus lived alongside other horned dinosaurs like Centrosaurus, but they probably ate different plants to avoid competing.1

Fossils of Chasmosaurus include skin impressions, which are very rare and help scientists understand what its skin looked like.1

One specimen, ROM 843, is a nearly complete skeleton that shows how the dinosaur was built.1

Chasmosaurus had a short nose and a beak, and its frill was probably used for display or to attract mates.1

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

?How big was Chasmosaurus?

Chasmosaurus was about 4.3 to 4.8 metres (14 to 16 feet) long and weighed around 1.5 to 2 tonnes (3,300 to 4,400 pounds). That is about the size of a small car.1 2

?What did Chasmosaurus eat?

Chasmosaurus was a herbivore, meaning it ate plants. It had a horny beak and teeth for cropping and chewing plant material.2

?Did Chasmosaurus have feathers?

No, Chasmosaurus did not have feathers. It had scaly skin, and we know this because fossil skin impressions have been found showing large scales in rows.1

?Why did Chasmosaurus have a frill?

The frill was probably used for display, to attract mates, or to make the dinosaur look bigger. It had huge holes to make it lighter, so it was not much use for defense.1

?Could Chasmosaurus walk on two legs?

No, Chasmosaurus walked on all four legs. Its front legs were shorter than its back legs, but it was quadrupedal.2

?When did Chasmosaurus live?

Chasmosaurus lived during the Late Cretaceous Period, about 77 to 74 million years ago.1 2

?Where was Chasmosaurus found?

Fossils of Chasmosaurus were found in the Dinosaur Park Formation in Alberta, Canada. All excavated specimens come from that area.1

?Was Chasmosaurus related to Triceratops?

Yes, Chasmosaurus was a ceratopsid, so it was related to Triceratops. But Chasmosaurus was smaller and had a longer frill with big holes.1

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Myth buster

Myth: Some people think Chasmosaurus was a type of Triceratops.

Truth: Chasmosaurus was a different genus of ceratopsid dinosaur, with a much larger frill and smaller horns than Triceratops.1

For dino experts

Scientific name: Chasmosaurus
Named by: Lambe 19143
Group: Horned dinos
Family / clade: Ceratopsidae3
Classification: Ornithischia > Ceratopsia > Ceratopsidae3
Age of the rocks: 84 to 72 million years (Campanian)3
Rock formations: Dinosaur Park, Oldman, Judith River3
Countries: Canada, USA3
Fossil records: 21 in the Paleobiology Database3
Also known as: Eoceratops, Mojoceratops, Protorosaurus (older names now counted as the same animal)3
Discovery: The first Chasmosaurus fossil was found in 1898 by Lawrence Lambe in Alberta, Canada. He named it Monoclonius belli at first, but later changed the name to Chasmosaurus in 1914.1
Still debated: Scientists still debate whether some fossils belong to Chasmosaurus or to a separate genus called Mojoceratops.1 3

Where the facts come from

Chasmosaurus (en.wikipedia.org)
Chasmosaurus | Natural History Museum (nhm.ac.uk)
Chasmosaurus in The Paleobiology Database (CC BY 4.0): age, places, rock formations, classification.

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