Pachychelium Stephensen 1925

• Main Authors: Lowry, J. K., Stoddart, H. E.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2012
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Amphipoda; Pakynidae; Pachychelium; Lowry; Pacific; Seta; Antarc*
• Online Access: https://zenodo.org/record/5251234; https://doi.org/10.5281/zenodo.5251234

Pachychelium Stephensen, 1925 Pachychelium Stephensen, 1925: 121. ― Schellenberg, 1926: 296. ―Schellenberg, 1931: 18. ―K.H. Barnard, 1932: 75. ―J.L. Barnard, 1969a: 354. ― Lowry, 1984: 99. ― Barnard & Karaman, 1991: 509. Type species. Pachychelium davidis Stephensen, 1925, by monotypy. Diagnostic description. Body shape slender. Head lateral cephalic lobe large, narrowly rounded. Antenna 1 peduncular article 1 without posterodistal spine; accessory flagellum article 1 long; [callynophore not known for female]. Mandible with accessory setal row absent; left lamina dentata absent; palp attached distally; palp article 2 broad, article 3 with subparallel margins or distally tapered. 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 3-articulate (article 4 absent). Gnathopod 1 ischium smaller than propodus; corner of palm with simple robust seta or without any robust seta. Gnathopod 2 palm obtuse. Epimeron 3 posteroventral corner broadly rounded. Uropod 3 biramous. Remarks. With the new species described from the boreal eastern North Pacific and the tropical western South Pacific and the reassignment of some species to Ultimachelium, the distribution of the previously bipolar genus Pachychelium is changed significantly. The sister taxon of Pachychelium appears to be Ultimachelium. The genera differ in the number of articles in the maxillipedal palp (article 4 absent in Pachychelium, large and well developed in Ultimachelium) and in epimeron 3 which has a broadly rounded posteroventral corner in Pachychelium, projecting and narrowly rounded in Ultimachelium. Species composition. Pachychelium davidis Stephensen, 1925; P. fucaensis sp. nov.; P. tropicalis sp. nov. Pachychelium antarcticum Schellenberg, 1926, is regarded as an unidentifiable taxon. Published as part of Lowry, J. K. & Stoddart, H. E., 2012, The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246, pp. 1-69 in Zootaxa 3246 (1) ...