Head to head
Snake vs Lizard
Every snake is descended from a lizard, which makes the two hard to separate cleanly, especially since there are legless lizards that look exactly like snakes. The reliable differences are in the eyes, the ears, and the jaw.
| Snake | Lizard | |
|---|---|---|
| Relationship | A branch that arose within the lizards | The broader ancestral group |
| Legs | None | Four in most; a few are legless |
| Eyelids | Fused, clear scale over the eye, cannot blink | Movable, can blink |
| Ear openings | None | Visible on each side of the head |
| Lower jaw | Two halves joined by stretchy ligament | A single rigid bone |
| Swallowing | Prey wider than the head, whole | Bite-sized prey, in most |
| Tongue | Deeply forked, flicked to smell | Forked in monitors and tegus, less so in others |
| Number of species | Around 4,000 | More than 7,000 |
Snake vs Lizard: common questions
If a snake has no legs, how do I tell it from a legless lizard?
Look at the head. A legless lizard, such as a slow worm or a glass lizard, still has movable eyelids, so it can blink, and it usually has a visible ear opening behind the eye, both of which a snake lacks entirely. Legless lizards also tend to have a blunt tail that can be shed and regrown, small even scales on the belly rather than the wide single row a snake uses to crawl, and a stiffer, less fluid way of moving. If the animal blinks at you, it is a lizard. If it stares with a fixed, lidless eye and a flicking forked tongue, and has broad belly scales, it is a snake.
Did snakes really evolve from lizards?
Yes, and the evidence is strong. Snakes sit firmly within the lizard family tree in every genetic analysis, closest to a group that includes monitor lizards or, by some studies, the anguimorphs and iguanians. Fossil snakes with small hind legs, such as Najash and Haasiophis, capture the transition, and living pythons and boas still have a vestigial pelvis and tiny external claw-like spurs where hind legs used to be. The debate now is not whether snakes came from lizards but which lizards, and whether the first snakes were burrowers or shallow-water swimmers, with current evidence leaning toward a burrowing or leaf-litter origin.
Are snakes or lizards more successful?
Both are doing very well, and together they make up the order Squamata, the largest group of reptiles by far. Lizards are more species-rich, with over 7,000 species to the snakes' roughly 4,000, and they occupy a wider range of diets, including many plant-eaters, which no snake is. Snakes have the edge in a few respects, spreading to more remote islands, colonising the open ocean as sea snakes, and reaching larger maximum sizes. Neither is replacing the other; the legless, wide-swallowing snake body plan simply opened a set of predatory niches that four-legged lizards could not exploit.