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Riojasaurus

Say it: ree-OH-hah-SORE-us

Name means: “lizard from La Rioja”1

Ate: PlantsLong-necksLate Triassic

Riojasaurus was a huge, plant-eating dinosaur with a long neck and a heavy body. It lived during the Late Triassic period in what is now Argentina. It probably walked slowly on all four legs, munching on leaves with its leaf-shaped teeth.1

Lived

227 to 206 million years ago4

Late Triassic

Fossils found in

La Rioja Province, Argentina (Los Colorados Formation)1 2

Food

Plants1

Length

6.6 to 10 m1

large individuals estimated to reach 10 m

Weight

800 kg to 3 tonnes1

When did it live?

Triassic

Jurassic

Cretaceous

252 million years ago20114566, the asteroid

How big was it?

as long as 2 cars parked in a rowas long as 56 bananas end to endas heavy as 2 carsas heavy as 100 big dogsas heavy as 600 watermelons

How big was Riojasaurus compared to YOU?

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cool stuff

Fun facts

Riojasaurus had very dense and massive leg bones, making it heavy and sturdy for an early sauropodomorph.1

Unlike most early relatives, Riojasaurus had four sacral vertebrae in its hip area instead of three, which helped support its weight.1

Its neck bones were longer than those of other sauropodomorphs found in the same formation, making its neck especially long.1

The first Riojasaurus skeleton found had no skull. A well-preserved skull was later discovered in 1987 and described in 1995.1

Some scientists think Riojasaurus may have been active at short intervals throughout the day and night, based on the shape of its eye bones (scleral rings).1

Riojasaurus is the only known riojasaurid dinosaur from South America, and it may be closely related to Melanorosaurus from southern Africa.1

Its front and hind limbs were nearly the same length, which is a clue that it walked on all fours and could not rear up on its back legs.1

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

?How big was Riojasaurus?

Riojasaurus was about 6.6 metres (21.7 feet) long and weighed around 800 kilograms (1,764 pounds). Some large individuals may have reached 10 metres (32.8 feet) long and weighed 3 metric tons (3.3 short tons).1

?What did Riojasaurus eat?

Riojasaurus was a herbivore that ate plants. Its leaf-shaped, serrated teeth were used for grazing on soft vegetation like gymnosperms, and it may have swallowed stones (gastroliths) to help grind food in its stomach.1 3

?Could Riojasaurus walk on two legs?

No, Riojasaurus probably walked on all four legs. Its front and hind limbs were nearly the same length, and its leg bones were dense and massive, suggesting it moved slowly on all fours and could not rear up on its back legs.1

?When did Riojasaurus live?

Riojasaurus lived during the Late Triassic Period, about 225 to 213 million years ago. Its fossils have been found in the Los Colorados Formation in Argentina.1

?Is Riojasaurus a dinosaur?

Yes, Riojasaurus is a dinosaur. It is a herbivorous sauropodomorph dinosaur from the Late Triassic of Argentina.1

?Did Riojasaurus have feathers?

No, there is no evidence that Riojasaurus had feathers. Its fossils show only scales and bones, and it is not known to have any feather-like structures.1

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For dino experts

Scientific name: Riojasaurus
Named by: Bonaparte 19694
Group: Long-necks
Family / clade: Riojasauridae4
Classification: Sauropodomorpha4
Age of the rocks: 227 to 206 million years (Norian)4
Rock formations: Los Colorados4
Countries: Argentina4
Fossil records: 2 in the Paleobiology Database4
Also known as: Strenusaurus (older names now counted as the same animal)4
Discovery: Riojasaurus was named by Argentine paleontologist José Bonaparte in 1969. The first skeleton (holotype PVL 3808) was found in 1966 in the Los Colorados Formation of La Rioja, Argentina. Later, many more skeletons and a skull were discovered.1 4
Still debated: Scientists disagree on whether Riojasaurus was completely quadrupedal or could sometimes walk on two legs. The hand and shoulder bones suggest it might have been able to move in different ways.1

Where the facts come from

Riojasaurus (en.wikipedia.org)
PBDB Taxon (paleobiodb.org)
Riojasaurus | Zoology | Research Starters | EBSCOhost (ebsco.com)
Riojasaurus 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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