taxonID	type	description	language	source
03ED1871FFAB9A79FF6BFF56FDC4FEF4.taxon	vernacular_names	[Japanese name: Tenrōyokoebi-ka]	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A79FF6BFEC2FD31FB94.taxon	type_taxon	Type species. Metarhachotropis parva sp. nov. by monotypy.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A79FF6BFEC2FD31FB94.taxon	diagnosis	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.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A79FF6BFEC2FD31FB94.taxon	etymology	Etymology. From the Greek meta (= beyond) and Rhachotropis (related genus).	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A79FF6BFEC2FD31FB94.taxon	discussion	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.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A7CFF6BFB4DFD2EFC4C.taxon	description	(Figs 1 – 4)	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A7CFF6BFB4DFD2EFC4C.taxon	materials_examined	Type material. Holotype: male, 2.1 mm (OMNH-Ar- 12515), west of Jōgashima Island in Miura City, Kanagawa Prefecture, 35 ° 08 ' 25 " N 139 ° 33 ' 42 " E – 35 ° 08 ' 19 " N 139 ° 33 ' 41 " E, 95 – 96 m depth, gravel and sand bottom, using dredge, 5 November 2015, coll. H. Kohtsuka. Paratype: male, 2.0 mm (OMNH-Ar- 12516), same data as holotype. Type locality. Sagami Bay, west of Jōgashima Island in Miura City, Kanagawa Prefecture, Japan.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A7CFF6BFB4DFD2EFC4C.taxon	etymology	Etymology. From the Latin parvus, - a, - um (= small), referring to the body size.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A7CFF6BFB4DFD2EFC4C.taxon	description	Description of male. Based on holotype (OMNH-Ar- 12515, 2.1 mm) and paratype (OMNH-Ar- 12516, 2.0 mm) only for mouthparts. Head (Figs 1, 2) large, rostrum developed. Eyes situated subventrally, ca. 1 / 3 length of head, composed of many dispersed ommatidia. Antenna 1 short, about 0.3 times of BL, weakly setose; peduncular articles 1 – 3 with length ratio of 1: 1.05: 0.45, article 1 stout, ventral margin lacking robust setae; accessory flagellum short, 1 - articulate, tip with 2 setae; primary flagellum with 4 articles, articles 2, 3 each with aesthetasc. Antenna 2 also short, weakly setose; peduncular articles 3 – 5 with length ratio of 1: 2.1: 2.25; flagellum with 4 articles. Upper lip with ventral margin rounded, bare. Mandibles, incisors with 2 cusps, laciniae mobilis 2 - toothed, wide in left and narrow in right, 3 accessory blades present, minute; molar columnar, poorly triturative; palp stout, article length ratio 1: 4.25: 5.0, articles 1, 2 lacking setae, article 3 with 2 – 3 short setae on tip. Lower lip wide, bare; mandibular processes large, inner lobes short. Maxilla 1 with inner plate lacking seta; outer plate with 4 robust setae apically; tip of palp article 2 with 4 short setae. Maxilla 2, inner plate wider and shorter than outer plate, both plates with several short setae distally. Maxilliped stout; inner and outer plates bearing 5 and 2 short setae, respectively; palp developed, medial margin of article 2 and distal margin of article 3 with 2 and 5 short setae, respectively. Pereon (Fig. 3). Gnathopod 1 large, poorly setose; coxa strongly projected anteroventrally; basis widened distally; merus short; carpus narrow, lobate posteriorly; propodus stout, palm oblique, smooth; dactylus curved posteriorly. Gnathopod 2 also large, poorly setose; coxa pentagonal, basis – dactylus similar to gnathopod 1. Pereopods 3, 4 slender, weakly setose; coxae subtriangular, gill on pereopod 4 wider than that on pereopod 3; dactyli almost linear. Pereopod 5 about 1.2 times as long as pereopod 4, weakly setose; coxa bilobed, posterior lobe deeper; basis relatively wide, subrectagular; propodus long; dactylus almost straight. Pereopod 6 about 1.05 times as long as pereopod 5, weakly setose; coxa bilobed, posterior lobe deeper; basis wide, subrectangular; propodus long; dactylus linear. Pereopod 7 ca. 1.15 times length of pereopod 6, weakly setose; coxa oval; basis expanded, posterodistal corner roundly projected; propodus long; dactylus straight. Pleon (Fig. 4). Epimeral plates, posteroventral corners of plates 1, 2 angular, that of plate 3 rounded, ventral margins without setae. Pleopods, pleopod 3 shortest; peduncles projected posterodistally, without setae; both rami short, outer rami longer than inner rami, outer and inner rami with 4 and 3 articles, respectively. Uropods relatively slender, outer rami shorter than inner rami, tips of both rami with minute embedded seta; length ratio of uropods 1 – 3 1: 0.9: 0.65. Telson elongate, cleft 38 % of telson length; lateral margins each with long sensory seta and short seta. Female. Unknown. Coloration in preservative (10 months after fixation). Eyes light brown. Body and appendages generally white.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A7CFF6BFB4DFD2EFC4C.taxon	discussion	Remarks. The uropods 1 and 2 with rami each bearing only minute embedded seta on the tip are also distinctive in the family Eusuridae sensu stricto. But discussion on the relationship with the senticaudate character is beyond the scope of this paper. Habitat. Gravel and sand bottom, 95 – 96 m depth.	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
03ED1871FFAB9A7CFF6BFB4DFD2EFC4C.taxon	distribution	Distribution. Japan: Sagami Bay (present study).	en	Ariyama, Hiroyuki, Kohtsuka, Hisanori (2022): Metarhachotropis parva, a new genus and species of Eusiridae (Crustacea: Amphipoda) from Sagami Bay, central Japan. Zootaxa 5188 (1): 95-100, DOI: https://doi.org/10.11646/zootaxa.5188.1.6
