The Squidasaurus Rex is a Tyrannosaurus rex-based dinosaur. It has Squidward's head and sharp teeth. Two fangs stick out of the mouth upwards when the mouth is closed. Like Squidward, it is turquoise in color. Instead of tentacles, it has the same limbs as a Tyrannosaurus rex. The neck also appears to get thinner towards the head. Despite its primal nature, it has shown to be intelligent enough to have emotion and speak in a deep British accent. It has also shown to have modern eating habits, but has trouble getting food to the mouth due to its small arms.
He first appears when Patrick takes Plankton's Time Machine for a joyride, accidentally thinking it was a photo booth (which the time machine was made out of). Patrick then returns to the present saying he has a message from the dawn of time and then tells everyone to run. The cephalopod/dinosaur bursts out of the time machine and does a short rampage as Squidward points at it and shouts its name in fear. He only stops when he and the others notice SpongeBob having a mental breakdown while mixing trash with recyclables. Later, during SpongeBob's execution he then says that he thought his people were primitive, since he is the only member of the group to not have a Krabby Patty and therefore did not get enraged like the rest. He makes a final appearance in the movie at the Krusty Krab trying to eat a Krabby Patty that can't reach his mouth. It is not known if he went home or stayed at Bikini Bottom after the events of the movie.
Video game appearance
He appears as the boss of the prehistory world in SpongeBob HeroPants. However, this time he is called Squidwardosaurus Rex. His main role in this game is making dinosaur noises and chasing after the player(s).
As stated by Squidward in SpongeBob HeroPants, Squidasaurus Rex is said to be a distant relative of Squidward.
In a deleted scene from The SpongeBob Movie: Sponge Out of Water, SpongeBob and Plankton encounter Squidasaurus Rex after time-traveling too far back in time.