Humongousaur (Species: Vaxasaurian) is one of the ten new alien forms that the 15-year old Ben gains from a recalibrated Omnitrix. He is the 3rd new alien that Ben uses. Humongosaur is a Vaxasaurian from the planet Terradino. Terradino is described as a postcard paradise with sandy beaches and thick jungles.
Humongousaur is twelve feet tall and can grow up sixty feet tall. His head is shown to be bigger than a child. He is a big, brown, somewhat humanoid alien, he has the symbol of the Omnitrix on his big, white, chest.
He has great strength and the ability to increase his body's size to 60 feet. He also becomes stronger as he grows. As he grows, he looks more and more dinosaur-like. Ben uses Humongousaur as his new "big gun" in place of Fourarms. He has also replaced Way Big, although he cannot grow as big.
Ben first transforms into Humugosaur in Ben 10 Returns (Part 2) when the Omnitrix is recalibrated. His first appearance in "Ben 10 Returns" is when Ben fights a swarm of Humongousaur is a Vaxasaurian dinosaur-like humanoid from Terradino (a play on terra which means earth and dino for dinosaur). Terradino is similar to Earth. It is a very beautiful planet, with all sorts of canyons, waters, rivers, plants and alien species. The only problem is that this Alien species always wage wars and fight each other. The species of Vaxasaurians are superior in the planet, because of their physical strength and power.