lepidosaurslizards

Lepidosaurs, a major clade of reptiles, include lizards, snakes, and the tuataras. They are united by distinctive features such as epidermal scales, a transverse cloacal opening, and the shedding of skin. The group comprises two primary lineages: Rhynchocephalia (tuataras) and Squamata (lizards and snakes). Lizards represent the largest living subgroup, occupying a wide range of habitats from deserts to forests and from ground level to tree canopies. Most lizards are terrestrial or arboreal and typically have four legs, but many lineages have reduced or lost limbs, including some legless lizards and snakes.

Anatomically, lepidosaurs generally have overlapping scales, a kinetic skull, and, in many species, external ear openings and movable eyelids, although some burrowing or aquatic forms have reductions. Snakes evolved from lizard-like ancestors and have highly specialized skulls and elongated bodies; tuataras are the closest living relatives of lizards outside Squamata.

The fossil record shows lepidosaurs first appearing in the late Permian, with major diversification in the Mesozoic. Today they are cosmopolitan, found on most landmasses except Antarctica, and display diverse diets and reproductive modes, including egg laying and live-bearing.

Conservation concerns focus on habitat loss, invasive predators, and climate change, which threaten many lizard and snake species worldwide.