Key to the genera of Gnathostenetroididae

1. Eyes present. Pleotelson posterolateral margins with indentations and posteriorly directed spines. Pleopod 4 exopod of one article, length about 0.5 endopod length.................................................................................................... Gnathostenetroides Amar, 1957 (12 marine species, shallow circumtropical coral reefs)

- Eyes absent. Pleotelson posterolateral margins rounded, without indentations and spines. Pleopod 4 exopod of two articles, not shorter than endopod................................................................................... 2

2. Body broad, flattened, length about 2.5–3.0 width. Endopod of pleopods 3 and 4 of two articles. Exopod of pleopod 3 narrower than endopod. Exopod of pleopod 4 as long as and broader than endopod.................................................................... Neostenetroides Carpenter and Magniez, 1982 (3 anchialine cave species from the Caribbean)

- Body elongate, vermiform, length about 9.0 width. Endopod of pleopods 3 and 4 of one article. Exopod of pleopod 3 as broad as endopod. Exopod of pleopod 4 longer than and not broader than endopod........................................ Caecostenetroides Fresi and Schiecke, 1968 (6 marine littoral interstitial species Japan, Mediterranean, Canary Islands, Ascension Island)