Mesosignum weddellensis Choudhury & Brandt, 2004, sp. nov.

• Main Authors: Choudhury, Madhumita, Brandt, Angelika
• Format: Other/Unknown Material
• Language: unknown
• Published: Zenodo 2004
• Subjects: Biodiversity; Taxonomy; Animalia; Arthropoda; Malacostraca; Isopoda; Mesosignidae; Mesosignum; Mesosignum weddellensis; Weddell Sea
• Online Access: https://doi.org/10.5281/zenodo.6272895; http://treatment.plazi.org/id/03E087F0FFEA4847FE89FE4FFB9EF93A

Mesosignum weddellensis sp. nov. (Figs. 1–4) Material examined: Holotype: 1 ɗ (2.0 mm), ZMH K40530, Weddell Sea; Station 135, 65°006’S, 43°119’W, depth 4677–4679 m, 11 March 2002, RV Polarstern . Also examined: Mesosignum asperum Menzies & Frankenberg, 1968, holotype ɗ (1.6 mm), AMNH 12494, Station: V–15–48, 10°07’N, 89°50’W, 3718 m, East Pacific, off Costa Rica, 21 November 1958. Mesosignum brevispinis Birstein, 1963, holotype (no registration number available) Ψ (1.6 mm), 48°50.8’N, 160°01.0’E, 5670–5680 m, Vityaz Station 3114, Kurile Islands, 1954; Mesosignum usheri (Menzies, 1962), holotype ɗ (2 mm), AMNH 12049, Station: V–15–13, 11°3’N, 75°3’W, 2875–2944 m, continental rise northwest of Cartegena, Colombia, 8 November 1958. Type locality: Weddell Sea, 65°006’S–43°119’W, 4677–4679 m. Diagnosis : Pereonite 1 without lateral extensions, pereonites 2 and 3 with long lateral extensions, with two branches, pereonite 4–7 only with one lateral extension. Posterodorsal part of the body with few small spines. Pleotelson oval, apex with 8 medial spines, slightly longer than wide, with 1 pair of lateral extensions on each side. Description (Fig.1 a): Body 1.4 times as long as wide; pereonite 1 as long as head and slightly broader, lateral margin smooth. Pereonites 2 and 3 with long lateral extensions, with 2 branches, anterior branch longer than posterior, pereonites 4–7 with only 1 lateral extension. Lateral extensions with spines. Anterior lateral extensions of pereonite 2–3 directed frontally. Pereonite 4 as long as pereonite 7, both longest segments. Pereonites 5 and 7 dorsal surface with very few short spines. Pereonite 5 laterally directed, pereonite 6–7 more or less caudolaterally directed. Pereonite 6 widest. Pleotelson oval, 0.3 as long as body, slightly longer than wide, with 16 lateral spines; lateral margins each with 2 lateral extensions, both directed posteriorly, anterior extension longer than posterior, at 0.5 length and posterior extension at 0.8 length. Antennula (Fig. 1 b): Peduncle with 3 ...