Grampusaurus is a fictional dinosaur. He appears in the "Dinosaur!" episode, where Oobi writes his own storybook called "The Lost Umasaurus." It is about a young dino named Umasaurus, who gets lost in the jungle. She tries to find her way back home to Grampusaurus, her grandpa. Grampusaurus is mentioned throughout the story, but doesn't appear until the end, when Umasaurus finally comes home and reunites with him. He hugs her and bakes delicious brownies ("dino snacks") for his granddaughter and her friends, Oobi-Rex and Dino-Kako.
Grampusaurus is a light green dinosaur with a few blue spots. He has many green-blue spikes along his back. Like the normal Grampu, he has hazel eyes and curls his fingers in an upright position.