Rex

Rexes are purple dinosaurs that live in Dinosaur Land and Hoohoo Mountain, first seen in Super Mario World. When Mario or Luigi stomps on a Rex's head the Rex will be flattened but not yet dead. He later appears in Mario & Luigi: Superstar Saga still possessing the "ability" to become flattened..

A Shroob version of Rexes (aptly named Shroob Rexes) appear in Mario & Luigi: Partners in Time in Shroob Castle.

Rex appears again in Super Princess Peach.