Pachychelium tropicalis Lowry &amp; Stoddart 2012, sp. nov.
Creators: name: Lowry, J. K.
name: Stoddart, H. E.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Amphipoda
Pakynidae
Pachychelium
Pachychelium tropicalis

description: <i>Pachychelium tropicalis</i> sp. nov. (Figs 23–25) <b>Type material.</b> HOLOTYPE, sex not known, 2.7 mm, AM P.46674, off Flynn Reef, Queensland, Australia, 16°37.81'S 146°23.08'E, 1000 m, trap sample with sediment, 5.2° C, J.K. Lowry, P. Freewater &amp; W. Vader, 6–7 June 1993, RV <i>Sunbird</i>, SEAS Project, stn QLD-930. <b>Type locality.</b> Off Flynn Reef, Queensland, Australia, 16°37.81'S 146°23.08'E, 1000 m depth. <b>Etymology</b>. The specific name reflects the unusual geographic position of this species. <b>Diagnostic description.</b> <i>Head</i> lateral cephalic lobe large, narrowly rounded; ventral margin curved. <i>Antenna 1</i> peduncular article 1 without posterodistal spine; accessory flagellum 2-articulate, article 1 long; flagellum with weak 1-field callynophore in specimen of unknown sex. <i>Mandible</i> lacinia mobilis absent; lamina dentata absent; accessory setal row absent; molar absent; palp attached distally; palp article 2 broad, shorter than article 3; article 3 with subparallel margins. <b> <i>Maxilla 1</i> outer plate with 6 setal-teeth</b> in 4/2 arrangement, one outer row setal-tooth with medial cusps; palp absent. <i>Maxilliped</i> inner plate absent; outer plate medium size; palp 3-articulate (article 4 absent), article 3 length 3.2 × breadth. <i>Gnathopod 1</i> subchelate; ischium smaller than propodus, not swollen posteroproximally; carpus extremely compressed; <b>propodus</b> length about 2 × breadth, posterior margin absent, <b>palm without produced posterodistal corner, without robust seta</b>. <i>Gnathopod 2</i> palm minute, obtuse. <i>Pereonite 4</i> without dorsal spines. <i>Pereonite 5</i> without dorsal spines. <i>Pereopod 5</i> merus without posteroproximal shoulder. <i>Pereopod 6</i> basis with posteroventral lobe weakly produced; merus longer than broad, without posteroproximal shoulder. <i>Pereopod 7</i> basis subovate with posterior margin smooth; merus, length of anterior margin 2.4 × proximal breadth. <i>Epimeron 3</i> posterior margin without projections, posteroventral corner broadly rounded. <i>Uropod 3</i> biramous, inner ramus just reaching base of article 2 of outer ramus. <i>Telson</i> longer than broad, entire. <b>Remarks.</b> Neither <i>P. tropicalis</i> nor <i>P. davidis</i> has a defining corner on the propodus of gnathopod 1. They differ in the length of the mandibular palp article 2 (shorter than article 3 in <i>P. tropicalis</i>, subequal in <i>P. davidis</i>); the shape of mandibular palp article 3 (parallel margins in <i>P. tropicalis</i>; tapering distally in <i>P. davidis</i>); and the basis of pereopod 5 (subquadrate in shape in <i>P. davidis</i>; subovate in <i>P. tropicalis</i>). <i>Pachychelium tropicalis</i> is the only species of the genus known to occur in the tropics and in the southern hemisphere. <b>Distribution.</b> North-eastern Australia, Coral Sea, western South Pacific Ocean; 1000 m depth.
description: Published as part of <i>Lowry, J. K. &amp; Stoddart, H. E., 2012, The Pachynidae fam. nov. (Crustacea: Amphipoda: Lysianassoidea) 3246, pp. 1-69 in Zootaxa 3246 (1)</i> on page 35, DOI: 10.11646/zootaxa.3246.1.1, http://zenodo.org/record/5249007