Rex is a Coelurosauravus. He was Insectosaurus' first creature.
Rex's card, along with the Move Cards Cyclone, Sonic Blast, and Air-Raid Storm, winded up outside London. He was activated when a windy day removed the dirt around his Capsule and blew it into a rock. He battled Panther, but lost due to the Element disadvantage. In the same episode, Dr. Cockroach determined him to be a 7 on the Power Scale. Three episodes later, he battled a Tylosaurus, along with five Ophthalmosaurus, and lost. The next episode, he battled a Hesperornis, along with the Ophthalmosaurus, and lost. Two episodes later, he was removed from Insecto's team to make room for Worm.
The first copy of the Cyclone Move Card was in Rex's Card Capsule, and was activated along with him.
The Sonic Blast Move Card was in Rex's Card Capsule, and was activated along with him.
The first copy of this powerful Move Card was in Rex's Card Capsule, and was activated along with him.
Rex has never won a battle.
There is also a Coelurosauravus called Rex in the British series Primeval.
Rex appeared outside London, the main setting of the aforementioned show.