Ankylosaurus, meaning "fused lizard", is a genus of armored dinosaur. Fossils of Ankylosaurus have been found ingeological formations dating to the very end of the Cretaceous Period, between about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs. It was named by Barnum Brown in 1908, and the only species classified in the genus is Ankylosaurus magniventris (magniventris meaning "great belly"). A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more extensive fossil material, Ankylosaurus is often considered the archetypal member of its group.
A female ankylosaurus first appeared in "Dinosaurs". Chris said that the tortoise reminded him of this dinosaur. After Zoboomafoo said the dinosaur's name, Chris added that she was the most heavily armored of all the dinosaurs; more than even Martin (who had medieval armor on at the time), who also stated that Ankylosaurus had the best protection on her (the spiky armor plates [osteoderms] on her back and the large club on her tail).
- Like other dinosaurs in the series, this species is computer animated (due to being extinct), making all individuals of the same species (male and female) look exactly the same.
- The other episodes showing this species reused the same footage from the first episode to show it.
- The Martinandchrisaurus had the tail of an Ankylosaurus.