New genera for species of Jassa Leach (Crustacea: Amphipoda) and their relationship to a revised Ischyrocerini Author Conlan, Kathleen E. text Zootaxa 2021 2021-02-03 4921 1 1 72 journal article 8297 10.11646/zootaxa.4921.1.1 6f7c2191-a210-4685-98f6-7a90241131df 1175-5326 4496015 2A77E821-52F4-450C-8964-7928D36C0906 Key to genera of the Ischyrocerini 1 Urosome 1 bearing 3 dorsal teeth or cusps ( Fig. 35a ).................................. Bathyphotis Stephensen, 1944 – Urosome 1 without dorsal teeth although there may be a pair of short setae ( Fig. 35b )............................... 2 2 Pereopods 5–7, ischium posteriorly winged ( Fig. 35c ). Uropod 3 uniramous, ramus ending in a cluster of spines ( Fig. 35e ).................................................................................. Alatajassa Conlan, 2007 – Pereopods 5–7, ischium not posteriorly winged ( Fig. 35d ). Uropod 3 biramous ( Fig. 35f )...............................3 3 Pereopods 3–4, propodus prehensile ( Fig. 35g )......................................... Isaeopsis K.H. Barnard, 1916 – Pereopods 3–4, propodus rectangular or oval and not expanded distally ( Fig. 35h ).....................................4 4 Coxa 4 posteriorly excavate ( Fig. 35i )........................................................................5 – Coxa 4 not posteriorly excavate (though it may be shallowly concave) ( Fig. 35j )......................................7 5 Gnathopod 1, carpus longer than the propodus (carpus:propodus length ~125%). Gnathopod 2, female, propodus massive, length ~175% the length of the propodus of gnathopod 1, palm toothed ( Fig. 35k )............. Veronajassa Vader and Myers, 1996 – Gnathopod 1, carpus subequal to or shorter than the propodus (carpus: propodus length ~45–95%). Gnathopod 2, female, propodus not massive, length ~125% the length of the propodus of gnathopod 1, palm not toothed ( Fig. 35l )....................6 6 Eyes absent. Maxilla 1, inner plate with a long apical seta ( Fig. 36a ). Coxa 1 more than half the depth of coxae 2–4. Gnathopod 1, carpus length ~95% the length of the propodus; propodus, palm shallowly excavate ( Figs 36c, d )................................................................................................. Myersius Souza-Filho & Serejo, 2014 – Eyes present. Maxilla 1, inner plate without a long apical seta ( Fig. 36b ). Coxa 1 ± half the depth of coxae 2–4. Gnathopod 1, carpus length ~45–50% the length of the propodus; propodus, palm convex ( Figs 36e, f )........... Microjassa Stebbing, 1899 7 Gnathopod 1, carpus ~100% the length of the propodus. Pereopods 3 and 4, dactyl ~175% the length of the propodus ( Fig. 36g )................................................................................ Scutischyrocerus Myers, 1995 – Gnathopod 1, carpus shorter than the propodus. Pereopods 3 and 4, dactyl ±90% the length of the propodus ( Fig. 36h )........8 8 Uropod 3 with a cluster of distolateral setae beside the outer ramus ( Fig. 36i ). Jassa group..............................9 – Uropod 3 without a cluster of distolateral setae beside the outer ramus Fig. 36j )......................................13 9 Antenna 1, accessory flagellum absent or scale-like ( Fig. 37a )................................ Parajassa Stebbing, 1899 – Antenna 1, accessory flagellum 2 articles, the second minute ( Fig. 37b )............................................10 10 Gnathopods and pereopods 3–4 clothed in abundant, long plumose setae ( Fig. 3 ). Gnathopod 2, either sex, propodus, palm bearing a central tooth and a second tooth at the palmar angle, with or without a single large spine at the palmar angle ( Fig. 37c )............................................................................................. Plumulojassa n. gen. – Gnathopods and pereopods 3–4, setae simple or finely pectinate except in the palm of the male gnathopod 2 where the setae may be plumose ( Figs 17 , 22 , 25 and 27– 29 ). Gnathopod 2, either sex, propodus, palm sinuous, concave or with a pronounced thumb defining the palm proximally, spines if present grouped in triplicate or if single, very small ( Figs 37 d–f)..................11 11 Gnathopods 1 and 2, propodus, palm defined by 1 spine. Gnathopod 2 without a gill. Pereopod 5, carpus with a cluster of spines posterodistally. Pleopods, rami very short, length ± depth of the pleon ( Figs 22–28 )....................... Pleojassa n. gen. – Gnathopods 1 and 2, propodus, palm defined by multiple spines (usually 3–4). Gnathopod 2 with a gill. Pereopod 5, carpus not spinose posterodistally. Pleopods, rami long, length> depth of the pleon ( Fig. 17 )....................................12 12 Gnathopod 2, propodus, both sexes producing a thumb at adulthood, palmar defining spines, if present, at the thumb tip ( Fig. 37e ), juvenile palm sinuous, without a thumb; pereopods 3 and 4, carpus <25% overlapped by the merus; uropod 3, outer ramus with many minute cusps proximal of the dorsally recurved terminal spine but without additional larger cusps ( Figs 17–21 )............................................................................................. Hemijassa Walker, 1907 – Gnathopod 2, propodus, only the male producing a thumb at adulthood, palmar defining spines, if present, proximal of the thumb tip ( Fig. 37f ), juvenile palm concave or sinuous, without a thumb; pereopods 3 and 4, carpus 80–100% overlapped by the merus; uropod 3, outer ramus with 2 (usually) larger cusps in addition to minute cusps proximal of the dorsally recurved terminal spine ( Figs 35b,d,f,h , 36 h,i and 37f )................................................................ Jassa Leach, 1814 13 Uropods 1, 2 and/or 3, peduncle with lateral row of setae ( Fig. 37g )..................... Ruffojassa Vader and Myers , 19961 – Uropods 1, 2 and/or 3, peduncle without a lateral row of setae...................................................14 14 Antenna 1, accessory flagellum 3–4 articles, the last minute. Uropod 3, outer ramus with one to several medial setae projecting dorsally ( Fig. 37h )................................................................ Ventojassa J. L. Barnard, 1970 – Antenna 1, accessory flagellum 1–2 articles, the last minute. Uropod 3, outer ramus without medial setae projecting dorsally.........................................................................................................15 15 Gnathopod 1, carpus longer than the propodus (carpus ~120% of the propodus length). Known only from subantarctic islands and Brazil , 44–1058 m ......................................................... Pseudischyrocerus Schellenberg, 1931 – Gnathopod 1, carpus shorter than the propodus (carpus ~50–95% of the propodus length). Various locations and depths......16 16 Mandibular palp, article 3 slender, ventrally convex and broadest centrally, tip acute ( Fig. 37i ). Antennae 1 and 2, length Ξ85% of the body length (headlobe to end of uropods), antenna 2 not stouter than antenna 1. Pereopods 3 and 4, merus not overlapping the carpus anteriorly. Uropod 2, outer ramus, length 65% of the inner ramus....................... Paradryope Stebbing , 18882 – Mandibular palp, article 3 broad distally, end rounded ( Fig. 37j ). Antennae 1 and 2, length ±65% of the body length (headlobe to end of uropods), antenna 2 stouter than or similar to antenna 1. Pereopods 3 and 4, merus overlapping 10–100% of the carpus. Uropod 2, outer ramus, length 75–80% of the inner ramus.......................................................17 17 Adult male gnathopod 2 grossly lengthened and pendulate, length 190–350% of the length of gnathopod 1, propodus slender, length 180–400% of its width at the centre, dactyl 50–100% of the length of the propodus ( Figs 38 a-c). Uropod 3 with 1–2 rows of mid-dorsal spines but without a corona of multiple spines on the distal margin ( Fig. 38d ). Warm temperate and tropical, Northern and Southern Hemisphere , known from 9– 40°N and 5– 34°S , 0–16 m depth ................... Neoischyrocerus Conlan, 1995 – Adult male gnathopod 2 variable in length but not pendulate, length 100–220% of the length of gnathopod 1, propodus variably slender or stout, length 120–290% of its width at the centre, dactyl 33–75% of the length of the propodus ( Figs 38 e-g). Uropod 3 with 1–2 rows of mid-dorsal spines and a corona of numerous spines on the distal margin 3 ( Fig. 38h ). Cold temperate and polar, primarily Northern Hemisphere, known from 36– 81°N and 42°S , 1–2000 m depth............... Ischyrocerus Krøyer, 1838