The Ouachita madtom (Noturus lachneri) is a catfish of the family Ictaluridae.The first specimens of the species were collected in 1952 it was not until 1969 that they were recognised as a species. The Ouachita madtom is similar to the tadpole madtom except the Ouachita madtom has one internasal pore while the tadpole madtom has two, and 16 to 18 anal rays while the tadpole madtom has only 14 to 16. It is also similar to the slender madtom but differing in the sack of serrae on the pectoral spine, having more caudal rays, and usually eight pectoral rays while the slender madtom has 9. The maximum length of an Ouachita madtom is about 2.7 inches.