Ultimachelium, Lowry & Stoddart, 2012

Lowry, J. K. & Stoddart, H. E., 2012, The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246, Zootaxa 3246 (1), pp. 1-69 : 62

Ultimachelium gen. nov.

Type species. Ultimachelium tac sp. nov.

Etymology. The generic name is contrived.

Diagnostic description. Body shape slender. Head lateral cephalic lobe large, broadly or narrowly rounded. Antenna 1 peduncular article 1 without posterodistal spine; accessory flagellum article 1 long; flagellum with callynophore in female. Mandible with accessory setal row absent; left lamina dentata absent; palp attached distally; palp article 2 broad, article 3 with subparallel margins or tapered distally. Maxilla 1 outer plate setal-teeth smooth, at least one inner row setal-tooth absent; palp absent. Maxilliped inner plate absent; outer plate medium size; palp 4-articulate, article 4 large. Gnathopod 1 ischium slightly smaller than, subequal to or larger than propodus; corner of palm without robust seta. Gnathopod 2 palm obtuse. Epimeron 3 posteroventral corner projecting, narrowly rounded. Uropod 3 biramous.

Species composition. Ultimachelium contains four species: U. barnardi ( Alonso de Pina, 1993) ; U. nichollsi ( Lowry, 1984) ; U. schellenbergi ( Lowry, 1984) ; U. tac sp. nov.

Remarks. Species in Ultimachelium were previously assigned to Pachychelium . In our view the old concept of Pachychelium is a complex of three genera: Pachychelium in the North Atlantic and North Pacific with one species in the deep-water tropics of north-eastern Australia; Smaraldia , a monotypic genus currently confined to southern temperate Australia; and Ultimachelium in southern South America and the Antarctic.