Ankylosaurus

Ankylosaurus was a genus of dinosaur belonging to the Ornithichian order, indigenous to planet Earth millions of years ago during the Cretacecous period. 23rd century paleontology believed that Ankylosaurs prefered dry environments and upland areas.

Description
Ankylosaurs walked on all four legs and were covered in bony armor plates. Their armor covered their skulls, including eyelids, their backs and long tails, at the end of which was a fused knot of bone that was used as a defensive weapon. The adults were around 6-7 meters in length.

Notable examples
After they had time travelled back to the late-Cretaceous via the Guardian of Forever, a landing party including Captain Kirk, Commander Spock and Doctor McCoy witnessed several families of Ankylosaurs and Pachycephalosaurs. The Ankylosaurs formed a defensive circle, with their young and the Pachycephalosaurs protected in the centre, during an attack by dozens of Troodons. The adult Ankylosaurs were ignored by the Troodons but when their defenses were breached, the group fled leaving their dead and wounded to their attackers.