The worm lizards, Amphisbaenidae, have been considered to belong to their own suborder of Squamata (Amphisbaenia) by some authors. Recent molecular studies have found them to be nested within the Sauria, and are derived from the Lacertidae. They last shared an ancestor with the Lacertidae about 139 Ma (139-115 Ma). There are six families of worm lizards and the Amphisbaenidae are relatively new, last sharing an ancestor with the Trogonophidae about 38 Ma (39-27 Ma). The family contains 19 genera and about 150 species. Worm lizards occur in the West Indies, South America, southern Europe, the Middle East, and Africa. They are limbless burrowers, have reduced eyes, have lost the right lung, most lay small clutches of eggs, and they are carnivorous. The scales are arranged in rings and most have one ring of scales for each vertebrae. The tails are blunt, and often have a superficial resemblance to the head, giving rise to the common name "two headed snakes." Keep in mind that while the common name "snake" may be applied to these animals they are not snakes. However, like the snakes they are nested within the lizards, but distinct from the snakes.

The Bachac Snake , Amphisbaenia alba Linnaeus 1758. The largest worm lizard reaches at least 700 mm. Photographed in Trinidad. The species ranges across most of northern South America, and may extend into Panama. It inhabits forest and savanna and is often associated with leaf-cutter ants nests. They may use the refuse pits of the ant nests to forage for rhinoceros beetle grubs.

Black and White Worm Lizard, Amphisbaenia fuliginosa Linnaeus 1758. Photographed in Trinidad. This animals was found under husks of coconut debris a few hundred feet from the beach. This is a widespread species ranging from Panama to Peru and Brazil. It reaches 425 mm and uses damp habitats in forest and savanna. Food includes a variety of invertebrates.