The Squidasaurus Rex is a Tyrannosaurus rex-based dinosaur. He has Squidward's head and sharp teeth. Two fangs stick out of his mouth upwards when it is closed. Like Squidward, he is turquoise. Instead of tentacles, he has the same limbs as a Tyrannosaurus rex. The neck also appears to get thinner towards the head.
Despite his primal nature, Squidasaurus Rex has shown to be intelligent enough to have emotion and speak in a deep English accent. He also seemed to recognized that habits of the citizens of Bikini Bottom were no better than its primitive kind. The Squidasaurus Rex has also shown to have modern eating habits, but has trouble getting food to the mouth due to his small arms. He is the first living Squid-saur (Squid face and dinosaur body). He doesn't reveal why his other family is not a Half-Dinosaur.
Role in movie
He first appears when Patrick accidentally 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 quickly 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.
The Squidasaurus only stops when he and the others notice SpongeBob having a mental breakdown while mixing trash with recyclables. Later, at SpongeBob's execution it is among the audience where it looks around at the cheering crowd and reveals that it can speak, as it says that he thought his friends were primitive, since it is the only member of the group to not have a Krabby Patty and therefore did not get enraged like the rest of the town.
He makes his final appearance in the movie at the Krusty Krab, trying to eat a Krabby Patty since his arms are too small that they can't reach his mouth. It is unknown if he went home to his own time period or if it stayed in Bikini Bottom after the events of the movie.
Role in SpongeBob HeroPants
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.
Because of this, he most likely comes before Squog.
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.
This was changed to Patrick going back in time and bringing the Squidasaurus Rex with him to the present.