The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246 Author Lowry, J. K. Author Stoddart, H. E. text Zootaxa 2012 2012-03-23 3246 1 1 69 https://biotaxa.org/Zootaxa/article/view/zootaxa.3246.1.1 journal article 10.11646/zootaxa.3246.1.1 1175­5334 5249007 Ultimachelium nichollsi ( Lowry, 1984 ) ( Figs 44 , 45 ) Pachychelium antarcticum . ― Nicholls, 1938: 14 , fig. 3. ― Bellan-Santini, 1972: 215 , pl. 28. ― Lowry & Bullock, 1976: 101 (in part). ― Lowry, 1982: 320 . Pachychelium nichollsi Lowry, 1984: 103 . ― Barnard & Karaman, 1991: 510 . ― De Broyer & Jazdzewski, 1993: 72 . Ultimachelium nichollsi . ― De Broyer et al ., 2007: 158 . Material examined. One ?female, 12 mm , USNM 1156710 , off South Georgia , Southern Ocean , 54°51'S 35°03'W , 168–173 m , trawl, 10 December 1986 , Professor Siedlecki , USARP cruise 601, stn 74. –1?male, 10.0 mm, USNM 1157037 , unknown locality, stn AH 4-30. –1?male, 11.5 mm , USNM 1157039 , unknown locality, stn AH 4-40 . Diagnostic description. Head lateral cephalic lobe large, narrowly rounded; ventral margin subsigmoidal. Antenna 1 peduncular article 1 without posterodistal spine; accessory flagellum 2-articulate, article 1 long; flagellum with strong callynophore in specimens of unknown sex. Mandible lacinia mobilis absent; lamina dentata absent; accessory setal row absent; molar absent; palp attached distally; palp article 2 broad, as long as article 3; article 3 tapered distally. Maxilla 1 outer plate with 6 setal-teeth in 3/3 arrangement, setal-teeth smooth; palp absent. Maxilliped inner plate absent; outer plate medium size; palp 4-articulate, article 4 large. Gnathopod 1 subchelate; ischium smaller than propodus ; merus with anterior margin ; carpus extremely compressed; propodus length about 1.9 × breadth, posterior margin extremely reduced, with produced corner, corner of palm without robust seta; dactylus reaching to corner of palm. Gnathopod 2 palm minute, obtuse. Pereonite 4 without dorsal spines. Pereonite 5 without dorsal spines. Pereopod 5 merus without posteroproximal shoulder. Pereopod 6 basis with posteroventral lobe weakly produced; merus longer than broad, without posteroproximal shoulder. Pereopod 7 basis subrectangular, posterodistal corner subquadrate , posterior margin weakly dentate; merus, length of anterior margin 2.6 × proximal breadth . Epimeron 3 posterior margin without projections, posteroventral corner subacute. Uropod 3 biramous, inner ramus just reaching base of article 2 or extending beyond article 1 of outer ramus. Telson slightly shorter than broad, entire. Remarks. Ultimachelium barnardi and U. nichollsi both have six setal-teeth on the outer plate of maxilla 1 in a 3/3 arrangement. They differ in the shape of mandibular palp article 3 (subparallel sides in U. barnardi , tapering distally in U. nichollsi ); and gnathopod 1 ischium (swollen posteroproximally in U. nichollsi , not swollen in U. barnardi ). Distribution. South Georgia , Southern Ocean and Adelie Coast, Antarctica ; 46–732 m depth.