Download FACT SHEET: riojasaurus

FACT SHEET: riojasaurus
NAME: RIOJASAURUS (ree-OH-cha-SAW-rus), meaning: “La Rioja lizard”
SIZE: 30 - 36 feet long (the size of a school bus)
TYPE OF DIET: Herbivore (plant leaves)
WHEN: Mid Triassic period (225 - 219 million years ago)
WHERE: Northwestern Argentina, South America
Riojasaurus lived about 225 to 219 million years ago. It was one of the earliest of the large
herbivores, or the great, plant-eating dinosaurs. We know a lot about this dinosaur because we
have found the bones of more than 20 different creatures. It was a heavily-built dinosaur, about
30-36 feet long. That’s about as long as a school bus! It grew very large for such a primitive, or
simple, dinosaur. Riojasaurus walked on four legs instead of two. It needed all four legs to hold up
its big, heavy body.
By studying the bones in its ankle, we believe that Riojasaurus was not able to stand up on
its back legs to look for food in trees. It probably couldn’t run on its back legs either. The back legs
were only slightly bigger than the front legs. The front legs were a little bit shorter, and this meant
that its head was close to the ground. This was good for eating the ferns and other plants that grew
low. Riojasaurus also had a long, flexible neck, so it could reach up into tree branches for food if it
needed to.
Its skull was very small and light. It had to be: if its head were heavier, Riojasaurus wouldn’t
be able to hold it up on its long neck. A small skull usually means a small brain. This means that
Riojasaurus was not a very intelligent dinosaur. It had
spoon-shaped, serrated teeth that looked like small saws.
The vertebrae, or bones in its neck and back, were hollow.
This made it much lighter and easier to move. An almost
complete Riojasaurus skeleton was found in northwest
Argentina, in a place called “La Rioja”. Its name means
“lizard from La Rioja”.
Dinosaur Days TM © 2010 Distant Train, inc. (www.distanttrain.com) all rights reserved