Tenontosaurus

Say it: ti-NON-tuh-SORE-us

Name means: “sinew lizard”1

Ate: PlantsBeaked plant-eatersEarly Cretaceous to Late Cretaceous

Tenontosaurus was a big plant-eating dinosaur with a very long, stiff tail. It lived in North America during the Early Cretaceous period, about 115 to 108 million years ago.1

Lived

121 to 94 million years ago3

Early Cretaceous to Late Cretaceous

Fossils found in

Fossils have been found in Montana, Wyoming, Oklahoma, Texas, Idaho, Utah, and Maryland in the USA, and also in Canada.1 2

Food

Plants1 2

Length

7 m2

Weight

900 kg2

Artist's life restoration of Tenontosaurus — How Tenontosaurus may have looked, by Nobu Tamura (http://spinops.blogspot.com). CC BY 2.5, via Wikimedia Commons. Scientists still argue about colours and details.

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

cool stuff

Fun facts

Tenontosaurus had an unusually long and broad tail, stiffened by a network of bony tendons, which is why it is called 'sinew lizard'.1

An adult Tenontosaurus could reach a browsing height of about 3 meters (10 feet) if it stood on its hind legs, but it usually walked on all fours.1

Its beak was U-shaped and thick, and its lower jaw had a special bone called a predentary that helped form the lower beak.1

Tenontosaurus lived alongside the predator Deinonychus, and fossils of both are common in the same rocks.1

The first Tenontosaurus fossil was found in 1903 in Montana, but it was not named until 1970.1

There are two species: Tenontosaurus tilletti and Tenontosaurus dossi. T. dossi is known from only a few specimens in Texas.1

Myth buster

Myth: Some people think Tenontosaurus was a slow, clumsy dinosaur.

Truth: Scientists think it was a common and successful herbivore, and its stiff tail may have helped it balance.1

For dino experts

Scientific name: Tenontosaurus
Named by: Ostrom 19703
Group: Beaked plant-eaters
Family / clade: Tenontosauridae3
Classification: Ornithischia > Ornithopoda > Iguanodontia3
Age of the rocks: 121 to 94 million years (Aptian to Cenomanian)3
Rock formations: Cloverly, Antlers, Cedar Mountain3
Countries: USA3
Fossil records: 83 in the Paleobiology Database3
Discovery: The first fossil was found in 1903 by an American Museum of Natural History expedition in Montana. John Ostrom named it Tenontosaurus tilletti in 1970 after studying many specimens.1
Still debated: Scientists still debate exactly how Tenontosaurus moved, whether it was mostly quadrupedal or could run on two legs.1

Where the facts come from

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