The hingemouth (Phractolaemus ansorgii) is a small freshwater fish that is found only in west central Africa, the sole member of the family Phractolaemidae of the family Kneriidae.

The mouth can extend like a small trunk, thus the name, and has just two teeth, both in the lower jaw.

Its mouth can extend up to 30% of the hingemouth's head length.

It has highly flexible lips, and its mouth is mainly supported by cartilage and other connective tissues.

[2] The swim bladder has two compartments, and can function as a lung, allowing the hingemouth to survive in oxygen-poor environments.