The helmeted water toad, Chilean helmeted bull frog or wide-mouth toad (Calyptocephalella gayi, syn. Caudiverba caudiverba) is the sole species of the genus Calyptocephalella in the family Calyptocephalellidae. The only other members of this family are Telmatobufo. The helmeted water toad is found in central Chile, and possibly adjacent west-central Argentina. This very large toad weighs up to 0.5 kg (1.1 lb). It is aquatic and found in deep ponds and small reservoirs. It is threatened by capture for human consumption, habitat loss, pollution, and introduced trout. It is occasionally captured for herpetoculture.