; class Amphibia, order Urodela)
A family of amphibians which have a broad head, the tongue free only at the sides, palatal teeth, costal grooves down the body, short, strong limbs, and a laterally compressed tail. Most burrow in earth for much of the year. Neoteny is common in some species, the best-known example being Ambystoma mexicanum (axolotl), confined to certain lakes around Mexico City, which normally breeds as an aquatic larva, but is capable of metamorphosis into a terrestrial form; it is sexually dimorphic, the female being the larger, attaining up to 29 cm in length, and normally black although albinos (see Albinism) are not uncommon. There are more than 30 species, found in N. and Central America.
Subjects: Zoology and Animal Sciences.