Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan Author Ariyama, Hiroyuki Osaka Museum of Natural History, Nagai Park, Higashi-Sumiyoshi, Osaka 546 - 0034 Japan. Author Kohtsuka, Hisanori 0000-0003-4440-2776 Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, 1024 Koajiro, Misaki, Miura, Kanagawa 238 - 0025 Japan. kohtsuka @ g. ecc. u-tokyo. ac. jp; https: // orcid. org / 0000 - 0003 - 4440 - 2776 kohtsuka@g.ecc.u-tokyo.ac.jp text Zootaxa 2022 2022-09-15 5188 1 95 100 journal article 147238 10.11646/zootaxa.5188.1.6 fc228778-e408-49cf-aed3-73078dac29b0 1175-5326 7087440 6EB3E7B3-990F-4AD5-B531-9CB1F4BFCD52 Genus Metarhachotropis , new [Japanese name: Kawari-ryūgūyokoebi-zoku, new] Type species. Metarhachotropis parva sp. nov. by monotypy. Diagnosis. Body weakly compressed laterally, smooth. Head massive, rostrum large, eyes present. Antennae subequal, without calceoli, accessory flagellum 1-articulate, flagella short. Mandible , molar poorly triturative. Maxillae reduced, palp of maxilla 1 ordinary, maxilla 2 inner plate broader than outer plate. Coxae very short, coxa 1 strongly produced anteriorly, coxa 4 lacking posterior excavation, coxae 5, 6 bilobed. Gnathopods alike, large, subchelate, not eusirid form; carpi narrow, with posterior lobe; propodi ovate, much longer than carpi, palms oblique. Pereopods slender; pereopods 3, 4 similar, bases narrow; pereopods 5–7 progressively longer, bases expanded. Pleonal epimeron 3 rounded. Uropods biramous, outer rami shorter than inner rami. Telson elongate, cleft. Etymology. From the Greek meta (= beyond) and Rhachotropis (related genus). Remarks. Metarhachotropis gen. nov. is characterized by the massive head with large rostrum. Despite the unique body shape, the keys to families in Barnard & Karaman (1991) lead the present specimens to Eusiridae sensu lato owing to (1) head massive but not downturned; (2) accessory flagellum 1-articulate; (3) mandibular palp present, molar well developed; (4) coxae 1–3 almost same length; (5) urosomites separate; (6) uropod 3 biramous, peduncle short, inner ramus not reduced; and (7) telson flat, elongate and cleft. Within the genera of the family, only Eusirella Chevreux, 1908 and Rhachotropis Smith, 1883 [both included in Eusiridae sensu stricto ( Lowry & Myers 2017 )] resembles this new genus in the very short coxae and the strongly produced coxa 1. However, Metarhachotropis can be distinguished from Eusirella by the large rostrum (small in Eusirella ) and the ordinary length of the maxilla 1 palp (short in Eusirella ), and from Rhachotropis by the smooth body (carinate or toothed in Rhachotropis ). Included taxa. Metarhachotropis parva sp. nov.