Flicking tongues. Unblinking stares. Incredible agility—but no visible arms or legs. The creatures surrounding you must be the planet's most intriguing, most misunderstood animals. They are squamates without limbs; you probably know them as snakes.

Over the course of evolution, limbs have vanished in the ancestors of many animal groups, including squamates. But snakes took life without limbs to a whole new level. Their uncanny traits—heat sensing and deadly venom, constriction and expandable jaws—arose during tens of millions of years spent adapting to a limbless lifestyle. Maybe that's why the 3,000 species of snakes fascinate us: they're among the most successful vertebrates on Earth.

SQUAMATE RELATIONSHIPS

This diagram shows the relationships among the snakes in this exhibit. It also includes the fossils on display. Overall, living snake species number about 3,000. Live snakes in this exhibit are shown by small photos; fossils displayed here are shown by name.

What this cladogram doesn't show is where snakes fit in squamates as a whole. That's because scientists still don't know which other squamates are the snakes' closest relatives. Skinks? Monitor Lizards? Extinct mosasaurs? Or could snakes be related to the common ancestor of all squamates? Stay tuned.