Dino card No. 0310 of 2,027

Brontomerus

Name means: “thunder thigh”1

Ate: PlantsLong-necksEarly Cretaceous

Brontomerus was a long-necked sauropod dinosaur with the biggest thigh muscles of any sauropod. Its name means 'thunder thigh' because its legs were so powerful. It lived about 110 million years ago in what is now Utah, USA.1

Lived

121 to 100 million years ago3

Early Cretaceous

Fossils found in

Hotel Mesa Quarry, Grand County, Utah, USA3 1

Food

Plants3

Length

4.5 to 14 m1

juvenile about 4.5 m, adult about 14 m

Weight

200 kg to 6 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 4 cars

as long as 3 cars parked in a rowas long as 78 bananas end to endabout as heavy as an elephantas heavy as 1200 watermelons

How big was Brontomerus compared to YOU?

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

cool stuff

Fun facts

Brontomerus had a hip bone that was very deep and had a front part much larger than the back part. This gave it the largest leg muscles of any sauropod.1

Scientists think Brontomerus used its powerful thigh muscles to kick predators or to walk over rough, hilly ground.1

The fossils were found in 1994 and 1995, but some bones had been stolen by private collectors. The remaining bones were even used to hold down a plastic tarp.1

Only two partial skeletons are known: one from a juvenile and one from a much larger adult. The adult may have been the mother of the juvenile.1

Brontomerus lived during the Early Cretaceous period, about 110 million years ago, in what is now Utah.1

The species name Brontomerus mcintoshi honors John Stanton McIntosh, a physicist and expert on North American sauropods.1

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

?How big was Brontomerus?

The adult Brontomerus was about 14 meters (46 feet) long and weighed around 6 tonnes. The juvenile was about 4.5 meters (15 feet) long and weighed about 200 kilograms.1

?What did Brontomerus eat?

Brontomerus was a sauropod, so it was a plant-eating dinosaur. It likely ate plants like ferns and trees.1 2

?Why did Brontomerus have big thighs?

Scientists think Brontomerus used its powerful thigh muscles to kick predators like Utahraptor, or to walk over rough, hilly ground. The muscles were probably not for running fast.1 2

?Was Brontomerus bigger than T. rex?

Brontomerus was about 14 meters (46 feet) long, which is longer than a T. rex, but T. rex was heavier and more bulky. Brontomerus was a long-necked plant-eater, not a predator.1

Ask Rex about Brontomerus

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Myth buster

Myth: Some people think Brontomerus was a fast runner because of its big leg muscles.

Truth: Scientists say the muscles were placed to move the leg forward powerfully or to kick, not for speed. The dinosaur probably used them for kicking or walking on rough terrain.1

For dino experts

Scientific name: Brontomerus
Named by: Taylor et al. 20113
Group: Long-necks
Family / clade: Somphospondyli3
Classification: Sauropodomorpha > Sauropoda > Macronaria3
Age of the rocks: 121 to 100 million years (Aptian / Albian)3
Rock formations: Cedar Mountain3
Countries: USA3
Fossil records: 1 in the Paleobiology Database3
Discovery: Brontomerus was named in 2011 by Michael P. Taylor, Mathew J. Wedel, and Richard L. Cifelli. The fossils were collected from the Hotel Mesa Quarry in Utah in 1994 and 1995.1 3
Still debated: Scientists are not sure exactly how Brontomerus used its huge thigh muscles. It might have kicked predators, walked on steep hills, or even stood on two legs for a short time.1

Where the facts come from

Brontomerus (en.wikipedia.org)
"Thunder Thighs" Dinosaur Thrashed Predators to Death? | National Geographic (nationalgeographic.com)
Brontomerus 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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