caecilian (sēsĭlˈēən) [key], any of the legless, tailless tropical amphibians belonging to the order Gymnophiona (or Apoda). Most adult caecilians resemble earthworms superficially but have vertebrate characteristics such as jaws and teeth.
Caecilians range in size from 7 in. to 4.5 ft (18 cm–140 cm); most are about 1 ft (30 cm) long. Their bodies are ringed with grooves, which in some species contain small scales imbedded in the skin; possession of scales is a primitive amphibian trait. There is a groove on either side of the head, each containing a retractable sensory tentacle. The eyes of caecilians are nearly functionless, and some species are eyeless.
Caecilians are found in swampy places in most tropical parts of the world, but are seldom seen because of their burrowing behavior. They eat small invertebrates such as termites and earthworms. A few species remain aquatic as adults and resemble eels.
There are more than 180 species of caecilians, divided into 10 families. They are classified in the phylum Chordata, subphylum Vertebrata, class Amphibia, order Gymnophiona (or Apoda).