Terrorsaur is one of the Predacons who work for Megatron. He was one of the original six Predacons who stole the Golden Disk. His beast form is a pterodactyl.
Terrorsaur often tried to take over as leader of the Predacons, blowing Megatron to bits at one point, but Scorponok repaired him.
When Megatron turned Rhinox into a Predacon, his aggressiveness caused him to attack Scorponok and Waspinator. Terrorsaur was interested in joining up with him and overthrowing Megatron, but Rhinox was not interested in working with him. This caused a fight to break out between Terrorsaur and Scorponok when Megatron sent them after Rhinox.
In Episode 27, "Aftermath", the premier of Season 2, Terrorsaur was seemingly killed along with Scorponok when the quantum surge caused them to collide on their hover platforms and fall into the lava pit. However a comic reveals that he survives and becomes a transmetal.
Terrorsaur is very similar to Starscream as both despise their leaders, plot against them and try to usurp their leadership.