What order of amphibians contains the limbless caecilians?

The order of amphibians containing the limbless caecilians is Gymnophiona.

Caecilians are one of the three major living amphibian lineages, alongside Anura—the frogs and toads—and Urodela, commonly called the salamanders. Their bodies are cylindrical and ringed, giving them a wormlike or snake-like appearance, but they are amphibians rather than reptiles. Most live hidden in tropical soil, leaf litter, or streambeds.

The name Gymnophiona comes from Ancient Greek words meaning “naked” and “snake.” Early naturalists sometimes suspected caecilians were related to snakes because of their elongated, limbless bodies and reduced eyes. Modern anatomy and genetics place them firmly within Amphibia. They have distinctive skulls, specialized jaw muscles, and small sensory tentacles between the eyes and nostrils.

Some references use Apoda as an alternative name, so it can appear in older classifications or specialist discussions. Gymnophiona is the standard modern answer, however, and is less confusing because Apoda has also been used for unrelated groups. More than 220 living caecilian species are currently recognized, spread across tropical parts of the Americas, Africa, and Asia.