Many groups of animals, from humans to dinosaurs to kangaroos, have evolved the ability to stand and walk on two legs. In all of these cases, the move from four legs to two has provided clear advantages. Kangaroos save energy because their hopping is so efficient, birds have freed their front pair of limbs for use as wings, and humans use ours for manipulating tools and objects.

But some species of lizards also rear up on their hind legs from time to time, particularly when running. The Australian frilled lizard does it so readily that it has earned the nickname of ‘bicycle lizard’. And the South American basilisk can move so quickly on its hind legs that it can even