A new generic name for the “Lepadichthys” lineatus complex with a rediagnosis of Discotrema, a senior synonym of Unguitrema, and comments on their phylogenetic relationships (Gobiesocidae: Diademichthyinae)

Rhinolepadichthys , a new genus of the gobiesocid subfamily Diademichthyinae, is described for the “ Lepadichthys ” lineatus complex (including Rhinolepadichthys geminus comb. nov. , R. heemstraorum comb. nov. , R. lineatus comb. nov. , and R. polyastrous comb. nov. ). Detailed investigation of external morphology and osteological anatomy of the new genus and related genera suggests that Rhinolepadichthys represents the sister genus to Discotrema , based on the following putative synapomorphies: (1) presence of a hardened (potentially keratinized) cap on the surface of at least some disc papillae (vs. surface of disc papillae soft, without hardened cap); and (2) the anterolateral part of the ventral postcleithrum extended anteriorly as a well-developed rod-like process, its tip close to the base of pelvic-fin soft ray 4 (vs. only weakly pointed, or irregular). Compared with Discotrema , Rhinolepadichthys gen. nov. is distinguished by the presence of a row of 8–12 large papillae on the inner surface of the upper and lower lips (vs. inner surface of lips smooth, without distinct papillae); the absence (vs. presence) of a well-developed lateral process on the pterotic immediately posterior to the opening of the otic canal; the presence (vs. absence) of gill rakers on the anterior edge of ceratobranchials 1–3; the presence (vs. absence) of gill rakers on the posterior edge of ceratobranchial 4; having the upper pharyngeal teeth arranged in a loose patch on the ventral surface of the pharyngobranchial 3 toothplate, with tooth tips directed posteroventrally (vs. arranged in a single row along posteroventral edge of the pharyngobranchial 3 toothplate, with tooth tips directed posteriorly); features of the adhesive disc, including outline of disc papillae roughly hexagonal or ovoid and with a flattened surface (vs. outline circular, at least some with raised, dome-like surface); the absence (vs. presence) of a deep cavity at the center of disc region C; the absence (vs. presence) of three paired and one median cluster of small papillae (reminiscent of bunches of grapes) across the surface of the adhesive disc; and having the ventral postcleithrum entire, not divided into two separate, articulating elements (vs. ventral postcleithrum divided into an anterior and posterior element, separated via a specialized joint). Reexamination of materials of the poorly known genus Unguitrema , considered a close relative of Discotrema , revealed no morphological differences between the two genera. Unguitrema therefore represents a junior synonym of Discotrema .