Pseudarachna Sars 1897

• Main Author: Merrin, Kelly L.
• Format: Text
• Language: unknown
• Published: Zenodo 2006
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Isopoda; Munnopsidae; Pseudarachna; Antarctic; The Antarctic; Lofoten; Norway; New Zealand; Bergen; Seta; Anvers; Anvers Island; Hicks; Fossa; Antarc*; Antarctica; North Atlantic
• Online Access: https://dx.doi.org/10.5281/zenodo.6257034; https://zenodo.org/record/6257034

Pseudarachna Sars, 1897 Mesostenus Sars, 1864: partim: 9 (preoccupied). Pseudarachna . — Sars, 1897: 142.— Nierstrasz & Schuurmans-Stekhoven, 1930: 129.— Kussakin, 2003: 261. Not Pseudarachna . — Schultz, 1976: 13. Type species: Mesostenus hirsutus Sars, 1864; by monotypy. Diagnosis Cephalic frons enlarged, broad, semi-circular, without defined ridge around antennae; cephalon anterior flanges absent. Pereonites 1–4 not short or compact, dorsal spines present, apical setae present. Pereonite 2 largest; pereonites 5–7, lateral margins not narrow, natasome not reduced. Pleon anterolateral margins rounded, without spine. Antennae positioned widely apart; antenna 1 small, article 1 with lateral flange; antenna 2 article 1 with no anterolateral spine. Mandible lacinia mobilis, spine row and palp all absent; mandibular fossa angular, sub-horizontal across mandible. Pereopod 2 elongate, robust; ischium compact, wider than other articles; pereopods 5 and 6 ischium superior margin with plumose setae; carpus paddle shaped; carpus and propodus with marginal plumose setae; pereopod 7 more ambulatory, with setation similar to that of pereopods 5 and 6; dactyli of natatory pereopods flattened, slightly broadened. Pleopod 4 exopod with more than 1 plumose seta. Pleon triangular, domed in centre. Operculum partially vaulted, with small medial keel. Pleopod 5 simple lobe. Uropods flat, uniramous. Remarks Pseudarachna has many unique apomorphies, the most notable being the enlarged, semi-circular shaped cephalic frons, the widely spaced antennae, the small antenna 1, enlarged pereonite 2 and a robust and enlarged pereopod 2 with a wide, compact ischium. Pseudarachna is easily distinguished by these characters from other closely related genera such as Ilyarachna Sars, 1870 and Echinozone Sars, 1897. Males are not known for this genus, and thus there is no data specific on sexual dimorphism. Distribution In the North Atlantic, from western Ireland to Denmark (Wolff 1962) at depths between 50–478 metres (Svavarsson et al . 1993); off eastern Australia at approximately 36 ° south and, Bass Strait at 38 ° south off Point Hicks (both records of undescribed mancas) at depths between 960–1277 metres; and the Challenger Plateau, west of the South Island, New Zealand at depths between 1005–1463 metres. : Published as part of Merrin, Kelly L., 2006, The first record of the crustacean isopod genus Pseudarachna Sars, 1897 (Isopoda: Asellota: Munnopsidae) from the Southern Hemisphere, with description of a new species from New Zealand, pp. 59-68 in Zootaxa 1370 on pages 60-61, DOI: 10.5281/zenodo.174907 : {"references": ["Sars, G. O. (1897) Isopoda. Part VII, VIII. Desmosomidae, Munnopsidae. (Bergen Museum: Bergen, Norway), 117 - 144.", "Sars, G. O. (1864) Om en anomal Gruppe af Isopoder. Forhandlinger i Videnskabs-Selskabet i Kristiania, 1863, 205 - 221.", "Nierstrasz, H. F. & Schuurmans-Stekhoven Jr, J. H. (1930) Isopoda genuina. Die Tierwelt der Nord- und Ostsee X. e 2, 57 - 133.", "Kussakin, O. G. (2003) Marine and brackishwater likefooted Crustacea (Isopoda) from the cold and temperate waters of the Northern Hemisphere. Suborder Asellota. Part 3 Munnopsidae (in Russian). (Izdatel'stvo Nauka: Leningrad), 380 pp.", "Schultz, G. A. (1976) Species of Asellotes (Isopoda: Paraselloidea) from Anvers Island, Antarctica. In: Biology of the Antarctic Seas VI. Antarctic Research Series 26, 1 - 35.", "Sars, G. O. (1870) Nye Dybuandscrustaceer fra Lofoten. Forhandlinger i Videnskabs-Selskabet i Kristiania, 1869, 145 - 286.", "Wolff, T. (1962) The systematics and biology of bathyal and abyssal Isopoda Asellota. Galathea Report, 6, 1 - 320.", "Svavarsson, J., Stromberg, J. O., & Brattegard, T. (1993) The deep-sea asellotes (Isopoda, Crustacea) fauna of the northern seas: species composition, distributional patterns and origin. Journal of Biogeography, 20, 537 - 555."]}