Ankylosaurus is an armored, herbivorous dinosaur. They lived in the Late Cretaceous period in western North America, along side with other famous dinosaurs such as Triceratops and T. Rex.
They had thick armor covering almost all of it's body, and have a bone crushing tail club, making it a dangerous dinosaur. They are aggressive, territorial and tend to attack animals that get close to them. Even with all it's protection it's scared of the gigantic baryonyx Rudy.
In the third movie, an Ankylosaurus appears to be the guardian or something of the portal entrance of the Dinosaur World, who welcomes the sub-zero heroes by attacking them, Crash and Eddie fake death and are about to be attacked by the Dino when Diego appears and saves them. In the end of the movie, when Rudy is chasing The Group, the Ankylosaurus is hiding and is scared. Diego turns back and calls the Ankylosaurus a Wuss, after turning and again started running.