Two new species of free-living marine nematodes of the family Oxystominidae Chitwood, 1935 (Enoplida) with a review of the genus Thalassoalaimus de Man, 1893 from the Argentine coast Author Martelli, Antonela Author Russo, Virginia Lo Author Villares, Gabriela Author Pastor De Ward, Catalina T. text Zootaxa 2017 4250 4 347 357 journal article 33288 10.11646/zootaxa.4250.4.5 f96392dc-e97b-41db-9607-31cf6cd2d050 1175-5326 495299 F15232E9-A0DF-4A72-94EE-40ACB7277A3C Thalassoalaimus de Man, 1893 , emended diagnosis Oxystominidae , Oxystomininae . Labial sensilla setiform, in circles of six inner and four or six outer on the anterior end. A circle of four cephalic setae more posteriorly. Amphideal fovea large and pocket-shaped. Males usually have papilliform precloacal supplements. Tail conical or conico-cylindrical. Thick cuticular lining, also called the caudal capsule, at the tail tip. Marine. Type species: T. tardus de Man, 1893 (8 species). Remarks. As was pointed out by Tchesunov et al. (2014) , the family Oxystominidae has two morphologically similar genera, Litinium and Thalassoalaimus . In their emended diagnosis of Litinium , one of the most important characters defining the genus is the absence of a caudal capsule. Hence, many putative species of Thalassoalaimus seem to be placed in the wrong genus because they have more characters of Litinium than of Thalassoalaimus . We present here revised species lists for both genera along with a list of species inquirendae for Thalassoalaimus .