Legless lizard

"Legless lizard" is a term used for several distinct groups of lizards that have either completely lost their limbs or reduced them to the point where they are useless for moving around. The name is also the common label for the family Pygopodidae. These reptiles can usually be told apart from snakes by a few key traits: they have eyelids, visible ear openings on the outside, no broad scales on their bellies, a tongue that is notched rather than forked, two lungs that are roughly the same size (snakes have one short lung and one very long one), and a tail that is very long compared to their body (snakes have a long body and a short tail).

Among limbless squamates, the shoulder girdle can be reduced in every possible way, even disappearing entirely, but the pelvic girdle never vanishes completely, no matter how much the limbs are reduced or lost. At the very least, the ilium bone remains in limbless lizards and in most primitive snakes. Limb reduction in Squamata is also strongly linked to body elongation, which usually happens through an increase in the number of vertebrae.

Many different lizard families have independently evolved limblessness or severely reduced limbs (which are probably not useful for locomotion). Examples include: Anguinae, a completely legless subfamily found in Europe, Asia, North America, and North Africa, which includes well-known animals like slow worms, glass snakes, and the scheltopusik; it belongs to the family Anguidae, which also has a legged subfamily called Gerrhonotinae. Cordylidae, an African family with 66 species, includes one nearly legless genus, Chamaesaura, whose five species have hindlimbs reduced to small, scaly bumps. Pygopodidae contains all 44 species, in the genera Aprasia, Delma, Lialis, Ophidiocephalus, Paradelma, Pletholax, and Pygopus.

They are all native to Australia, except for two Lialis species that also live in New Guinea (one of which is found only there). Pygopodids are not truly legless—they lack forelimbs but have hindlimbs reduced to small, fingerless flaps, which is why they are often called "flap-footed lizards" or "scaly-foot." They are considered an advanced evolutionary group within Gekkota, which also includes six families of geckos. Dibamidae includes all 23 species in the family, which consists of the single Mexican genus Anelytropsis and the Southeast Asian genus Dibamus; all are limbless burrowers that are nearly or completely blind. Anniellidae contains just the genus Anniella, with six legless lizards that live in central and southern California and Baja California, Mexico.

Ophiodes is a genus of legless lizard from South America, placed within the otherwise legged galliwasps (Diploglossidae). Gymnophthalmidae is a large neotropical family with many species that have reduced limbs; the most extreme are the 23 species in the genus Bachia, which escape by making sudden, springy "figure-8" flicks with their body and tail. Scincidae, commonly known as skinks, is the largest lizard family with over 1500 species, and many of these are limbless or nearly limbless, including (but not limited to) the African genera Acontias, Feylinia, Melanoseps, Paracontias, Scelotes, and Typhlosaurus; the Australian genera Lerista, Ophioscincus, Coeranoscincus, and Anomalopus; and some species in the genus Chalcides from southern Europe and North Africa. Amphisbaenia, commonly called worm lizards, includes 201 living species in 6 families, most of which are legless (hindlimbs are always absent): Amphisbaenidae, Bipedidae, Blanidae, Cadeidae, Rhineuridae, and Trogonophidae.