Description of two new species of Bassozetus (Ophidiiformes: Ophidiidae) and a redescription of Bassozetus robustus Smith and Radcliffe 1913

Abstract

Two new deepwater assfish species, Bassozetus trachibranchus and Bassozetus squamosus, are described from the 29 western Atlantic and four western Indian and western South Pacific specimens, respectively. In addition, a redescription of Bassozetus robustus Smith and Radcliffe in Radcliffe 1913, with which both of the above two new species have been previously confused, is provided on the basis of 14 specimens and its distributional range is revised to the western Pacific Ocean. The three species are separable from the 13 known congeners by the following combination of characters: dorsal-fin rays (116–126), anal-fin rays (95–103), oblique scale rows (30–47), pelvic-fin length (14.3–21.7% SL), a single well-developed median bashibranchial tooth patch, and one or two deep indentations on the sagitta dorsal margin, plus long gill rakers (10–14 in B. robustus) and head, predorsal and prepelvic lengths (20.5–22.8% SL, 19.4–21.1% SL and 15.3–18.1% SL, respectively, in B. robustus). Additionally, B. trachibranchus, B. squamosus and B. robustus are distinguishable from each other as follows: oblique scale rows (39–45 in B. trachibranchus, 44–47 in B. squamosus, and 30–36 in B. robustus), eye diameter to head length ratio (greater in B. squamosus than in similarly sized specimens of the other species), pelvic fin length/distance between pelvic and anal fins ratio (smaller in B. robustus than in similarly sized specimens of the other species), and 2nd to 4th lower limb morphology (many small tooth patches arranged along the outer ridges in B. trachibranchus, absent or a few only in the other species).