Monitor Lizard
Monitor Lizard is a female white-throated monitor (a subspecies of rock monitor [simply called a monitor lizard]) who appeared in the episode "Dinosaurs".  When Zoboomafoo first saw her, he thought she was a dinosaur. They way Monitor Lizard walked on 4 legs reminded Chris of the dinosaur Brontosaurus, and her sharp teeth reminded Martin of the dinosaur Tyrannosaurus Rex.  
Mystery Animal 3

Monitor Lizard as she appears in "Mystery Animal"