A new genus and species of Eusiridae (Crustacea, Amphipoda, Amphilochidea) from bathyal sediments off the southwestern Gulf of Mexico

Abstract

A new monotypic genus of eusirid amphipod, Pseudorhachotropis gen. nov., is described and illustrated from a male specimen collected from bathyal soft bottoms (2321 m depth) in the southern Gulf of Mexico. The new genus is morphologically close to the genus Rhachotropis, previously documented from bathyal and abyssal deep–water worldwide. The new eusirid differs from other genera in having antenna 1 with 5–articulate accessory flagellum, mandibular molar smooth conical protuberance with large robust setae, pereonal segments smooth, pleonal segments 1–3 posterodistal notched, urosomal segments 1–2 with large posterodorsal processes, coxa 1 quadrangular unproduced anteriorly, uropod 1 interramal robust seta, epimeron 3 with three teeth posteroventral corner, telson as long as wide, “V” inverted shape incised 0.3 x posterior margin, each lobe 1–2 robust setae, besides the most important character to distinguish such genus includes molar palp article 1 long, subequal in length to article 2. A comparative table showing primarily features of the 14 known genera of eusirid amphipods, is also given.