Most species of lizard are quadrupedal and crawl using their four limbs and tail. Certain species are legless and slither like snakes. Some lizards, such as geckos, can adhere to vertical or inverted surfaces and move freely on them.
Approximately 6,000 known species of lizard live worldwide, with the major exception of Antarctica. Lizards are closely related to snakes, and legless lizards are difficult to differentiate from snakes. One key difference between snakes and lizards is the presence of exterior ears, which snakes lack. In addition, legless lizards are unable to unhinge their jaws the same way that snakes can.