The Mexican mole lizard (Bipes biporus) is one of four amphisbaenians that have legs, and the only non-extinct species of animal to have only two limbs, apart from the Lesser and Greater Siren.
Their skin is closely segmented to give a corrugated appearance, and like earthworms, their underground movement is by peristalsis of the segments. The forelegs are strong and paddle-like, while the hindlegs have disappeared, leaving behind only vestigial bones visible in X-rays.