Why do some lizards have no legs?

In many lizard species, the loss of limbs is an evolutionary adaptation often associated with the elongation of the body. This transition typically occurs in groups that have adopted subterranean or burrowing lifestyles, where having legs may be a hindrance.12

For these limbless or reduced-limb lizards, locomotion is achieved through lateral undulations of the body, which are powered by complex ventral abdominal muscles. While some species move quickly across the surface, others are specialized for "swimming" through sand or digging into the substrate.1

Limb reduction has evolved independently across several groups of autarchoglossan lizards, such as skinks, glass lizards, and worm lizards (amphisbaenians). This evolutionary path is distinct from that of snakes, which are considered a highly specialized group of limbless lizards that evolved from terrestrial ancestors during the Early Cretaceous Epoch.1324