The caecilians s are an order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 (Gymnophiona) of amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s that superficially resemble earthworm
Earthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...

s or snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...

s. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

*Caecilian*Apoda, moth genus of the Limacodidae family...

. They are mostly distributed in the tropics of South America, Africa, and South Asia. The diet of caecilians is not well known.
Caecilians completely lack limbs, making the smaller species resemble worms, while the larger species with lengths up to 1.5 m (4.9 ft) resemble snakes.