负子蟾是多种分布于南美洲和非洲的原始蛙类。

完全水栖性。背、腹部平坦、身体流线形。后足蹼发达。皮肤光滑。有侧线系统。头小、无舌。眼睑无法自由移动。后足趾上有爪。

The Pipidae are a family of primitive, tongueless frogs. The 30 species in the family Pipidae are found in tropical South America (genus Pipa) and sub-Saharan Africa (four other genera).

These frogs are exclusively aquatic and have numerous morphological modifications befitting their habitat. For example, the feet are completely webbed, the body is flattened, and a lateral line system is present. In addition, pipids possess highly modified ears for producing and receiving sound underwater. They lack a tongue or vocal cords, instead having bony rods in the larynx that help produce sound. They range from 4 to 19 cm (1.6 to 7.5 in) in body length.