Legless lizard

Legless lizards are several different groups of lizards that have evolved to live without limbs. In these animals, limbs have been lost or reduced so much they cannot be used for locomotion. Locomotion is the way an animal moves from one place to another. This physical change often happens alongside body elongation. As these animals grow longer, they typically see an increase in their vertebral number. Vertebrae are the individual bones that make up the spine. This process of losing limbs has occurred independently in many different lizard families across the globe.

While they may look like snakes, legless lizards have several distinct physical traits. One major difference is the presence of eyelids. Most snakes lack eyelids, but legless lizards possess them to cover their eyes. You can also look for external ear openings on the side of the head. Snakes do not have these openings, but legless lizards do. Another way to tell them apart is by their lungs. Snakes usually have one short lung and one very long lung. In contrast, legless lizards typically have two lungs of roughly equal size. Finally, their body proportions differ. Snakes generally have long bodies and short tails, while legless lizards often have very long tails.

Even when limbs disappear, the internal skeleton remains partially intact. The reduction of the shoulder girdle can lead to its complete loss. However, the pelvic girdle, which is the part of the skeleton near the hips, is never completely lost. This remains true regardless of how much the limbs have been reduced. At least the ilium, a specific bone in the pelvis, is retained in limbless lizards and most basal snakes. This means that while the outside of the animal looks smooth, the internal structure still holds onto parts of its ancestral anatomy.

Many different families show these adaptations. The Anguinae subfamily is entirely legless and lives in Europe, Asia, North America, and North Africa. This group includes the slow worm and the glass lizard. In Africa, the Cordylidae family contains 66 species. One genus, Chamaesaura, is almost legless. It has five species with hindlimbs reduced to small, scaly protuberances. In South America, the genus Bachia belongs to the Gymnophthalmidae family. These 23 species use a unique movement to escape. They make sudden saltatory flicks, which are jumping-like motions, in a figure-8 shape using their bodies and tails.

The Pygopodidae are a unique group of 44 species found mostly in Australia. Two species of the genus Lialis are also found in New Guinea. These animals are not strictly legless. While they lack forelimbs, they have greatly reduced hindlimbs. These hindlimbs look like small, digitless flaps. Because of this, people often call them "flap-footed lizards" or "scaly-foot" lizards. Scientists consider pygopodids to be an advanced evolutionary clade of the Gekkota. This is the same group that contains six different families of geckos.

Some legless lizards have specialized lifestyles based on where they live. The Dibamidae family includes 23 species in Mexico and Southeast Asia. These are limbless burrowers, meaning they live and move through the soil. They are also nearly or completely blind. In California and Mexico, the Anniellidae family contains six legless species. There are also 201 species of worm lizards known as Amphisbaenia. These are organized into six families, such as Amphisbaenidae and Bipedidae. In most of these species, the hindlimbs are always absent.

The Scincidae family, commonly known as skinks, is the largest lizard family. It contains over 1,500 species. Many of these species are limbless or nearly limbless. You can find these lizards in many different regions. In Africa, genera like Acontias and Melanoseps show these traits. In Australia, you can find Lerista and Anomalopus. Some species in the genus Chalcides live in southern Europe and North Africa. This massive family shows how common and successful the legless body plan can be in the lizard world.