Heterenchelyidae

The Heterenchelyidae or mud eels are a small family of eels native to the Atlantic, Mediterranean, and eastern Pacific.

Heterenchelyids are bottom-dwelling fish adapted to burrowing into soft mud. They have large mouths and no pectoral fins, and range from 32 to 149 cm in length. Currently, eight species in two genera are recognized in this family.

The oldest known member of the family is Pythonichthys arkansasensis, known from fossilized otoliths from the Maastrichtian and Danian of the south-central United States.