The genus
Stenoninereis is newly recorded from Mexican waters. The only formerly known species of the genus,
Stenoninereis martini Wesenberg-Lung, 1958, is recorded from Laguna de Terminos, State of Campeche, Mexico, where it was found associated with mangrove roots.
Stenoninereis tecolutlensis n. sp. was collected in Tecolutla, State of Veracruz, under oyster shells attached to mangrove roots in an estuarine zone. Both specimens are described and illustrated, and a key is provided in order to distinguish between them.