Didogobius lanceolatus sp. nov., a new goby species from Mauritania, with diagnoses for two new gobiine genera (Teleostei, Gobiidae, Gobiinae)

Didogobius lanceolatus sp. nov. is described from a single specimen collected from the southern Banc d’Arguin, Mauritania. The species differs from all currently described congeners, as well as from all species of the closely related species of the genera Chromogobius and Gammogobius, by the combination of the following characters: (1) lanceolate caudal fin; (2) small (reduced) vs. large eyes; (3) 27 vertebrae; (4) D2 I, 13, A I, 11; (5) predorsal region in front of first dorsal fin D1 naked; (6) body squamation reduced, with only few areas on flank covered by externally visible cycloid scales behind pectoral origin and on caudal peduncle; (7) anterior oculoscapular canal present, with only pores σ, κ, α, ρ; (8) posterior oculoscapular and preopercular head canal absent; (9) suborbital row 7 close to pore α with more than five papillae; (10) suborbital rows 2 and 4 close to orbit; (11) interorbital papillae absent. The new species appears most closely related to the type species of Didogobius Miller 1966, D. bentuvii Miller, 1966, as it shares a set of apparently derived morphological characters, such as the lanceolate caudal fin, minute eyes and the anterior oculoscapular canal with only pores σ, κ, α, ρ present. Phylogenetic analysis of COI-barcoding data further suggests a close relationship with two other species of the genus Didogobius exclusively sharing with the new species and D. bentuvii elevated unpaired fin ray counts, i. e., D2 branched rays ≥ 12 (vs. ≤ 11 in all other species) and A branched rays ≥ 11 (vs. ≤ 10 in all other species); these two species are D. kochi Van Tassell, 1988 and D. schlieweni Miller, 1992. Based on the description of new Didogobius species obviously closely related to the type species of Didogobius, on re-examination of the single type specimen of D. bentuvii and on the new DNA barcoding data we restrict and re-diagnose the genus Didogobius to include only the aforementioned four species. The other former Didogobius species are placed in two new genera, each unambiguously diagnosable on previously established morphological data: Marcelogobius gen. nov. with M. splechtnai, M. helenae and M. janetarum, and Peter gen. nov. with the two shrimp-associated species P. amicuscaridis and P. wirtzi.