Humungousaur first appeared in Ben 10 Returns (Part Two). Humungousaur  is the second largest alien that Ben can turn himself into with the Omnitrix.

Humungousaur is 12 feet tall but can grow in size and strength. At his maximum height he is 60 feet tall and a force to be reckoned with.  With spikes on his tail and armoured plates on his body he resembles a dinosaur. Humungousaur’s super thick skin and strength give him great resistance to injury and even allow him to survive in space for a few minutes. Humungousaur can evolve into one of the ultimate aliens (Ultimate Humungousaur). Watch out for his Humungousaur Hands, as landing a single punch is sure to knock most enemies out.