Caecilians completely lack limbs, making the smaller species resemble worms, while the larger species with lengths up to 1.5 m (4 ft 11 in) resemble snakes. The tail is short or absent, and the cloaca is near the end of the body. The caecilians are an order (Gymnophiona) of amphibians that superficially resemble earthworms or snakes. 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 Apoda. They are mostly distributed in the tropics of South and Central America, Africa, and South Asia. The diet of caecilians is not well known.