Pachychelium antarcticum Lowry & Bullock, 1976: 101 Pachychelium davidis Barnard, 1932: 75 Pachychelium schellenbergi Lowry, 1984: 102 Barnard & Karaman, 1991:550 Gonzalez, 1991: 59 De Broyer & Jazdzewski, 1993: 74 Ultimachelium schellenbergi De Broyer et al ., 2007: 158 The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246 Lowry, J. K. Stoddart, H. E. Zootaxa 2012 2012-03-23 3246 1 1 69 7DGYW (Lowry, 1984) Lowry 1984 [151,681,1239,1265] Malacostraca Pakynidae Ultimachelium Animalia Amphipoda 63 64 Arthropoda species schellenbergi  ( Fig. 46)     Pachychelium antarcticum.―Schellenberg, 1931: 19, fig. 8. ―  Lowry & Bullock, 1976: 101(in part).  ?  Pachychelium davidis.―K.H.  Barnard, 1932: 75, fig. 32.     Pachychelium schellenbergi Lowry, 1984: 102, figs 39–41. ―  Barnard & Karaman, 1991:550. ―  Gonzalez, 1991: 59. ―  De Broyer & Jazdzewski, 1993: 74.    Ultimachelium schellenbergi. ―  De Broyer et al., 2007: 158.   Material examined.  Onespecimen,?male, 4.8 mm, SMNHno. 116349, Estero Huito, north of Punta Yahuecha, northern part of Golfo de Ancud, Chile, eastern South Pacific Ocean, 41°45'30"S 73°07'50"W,  35 m, dead algae, dredge or trawl,  15 December 1948, Lund University ChileExpedition, stn M18.  Diagnostic description. Headlateral cephalic lobe large, narrowly rounded; ventral margin curved. Antenna 1peduncular article 1 without posterodistal spine; accessory flagellum 2-articulate, article 1 long; flagellum without callynophore in female. Mandiblelacinia 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 1outer plate with 5 or 6 setal-teeth in 3/2 or 4/2 arrangement, setal-teeth smooth; palp absent. Maxillipedinner plate absent; outer plate medium size; palp 4-articulate, article 4 large. Gnathopod 1subchelate; ischium larger than propodus; merus without anterior margin; carpus extremely compressed; propodus length about 1.8 × breadth, posterior margin absent, palm with produced corner, corner of palm without robust seta; dactylus reaching to corner of palm. Gnathopod 2palm minute, obtuse. Pereonite 4without dorsal spines. Pereonite 5without dorsal spines. Pereopod 5merus without posteroproximal shoulder. Pereopod 6basis with posteroventral lobe weakly produced; merus as broad as long, without posteroproximal shoulder.  Pereopod 7basis subovate, posterodistal corner rounded, posterior margin weakly dentate; merus, length of anterior margin 1.9 × proximal breadth. Epimeron 3posterior margin without projections, posteroventral corner subquadrate. Uropod 3biramous, inner ramus just reaching base of article 2 of outer ramus.  Telsonas long as broad, entire.   Remarks.  Ultimachelium schellenbergiis a south-western South American species closely related to  U. tac. The main difference between these species is the size of the ischium of gnathopod 1, which is larger than the propodus in  U. schellenbergiand about the same size as the propodus in  U. tac.  Ultimachelium schellenbergiis a larger species (about 6 mm) known from shallower water (less than 35 m) than  U. tacwhich is about 3 mmin length and known from depths of 250 to 300 m. Unlike  U. schellenbergi,  U. tacdoes not have any slender setae along the anterior margins of pereopods 5 to 7.   Distribution.Southern Chile, eastern South Pacific Ocean; Magellanic area; South Georgiaand Falkland Islands, Southern Ocean; 1–35 mdepth. 1948-12-15 SMNH One & Estero Huito & de Ancud Chile eastern South Pacific Ocean 35 -41.758335 Punta Yahuecha 19 -73.130554 Golfo de Ancud 63 64 1