Oxypleurodon christiani, Forges, Bertrand Richer De & Corbari, Laure, 2012

Forges, Bertrand Richer De & Corbari, Laure, 2012, A new species of Oxypleurodon Miers, 1886 (Crustacea, Brachyura, Majoidea) from the Bismarck Sea, Papua New Guinea, Zootaxa 3320, pp. 56-60 : 57-59

Oxypleurodon christiani n. sp.

Figs 1 A–C; 2 A, B; 2 A.

Material examined: Papua New Guinea, Bismarck Sea, west of New Hanover I., BIOPAPUA, stn. CP 3653, 02 °13' S - 150°23' E, 680–700 m, 28/08/2010: male holotype 18.5 x 12.6 mm (MNHN-IU-2011-3891) S. Samadi & L. Corbari coll.

Diagnosis: Carapace triangular. Rostrum composed of 2 flattened, ear-shaped horns which are closely clustered. Carapace with raised plates arranged as follows: 2 semicircular supraocular plates; 1 gastric plate composed of 2 parts, long slender anterior gastric part connected with small posterior transverse part; 1 cardiac plate regularly curved, connected to posterior border of carapace, forming typically mushroom-shaped structure; 2 large branchial plates fused with 2 hepatic plates ( Fig. 1 A, 2A); branchial plate with deep notch on interior side ( Fig. 1 ).

Eyes small with dark, round cornea, protected by anterior part of hepatic plate. Antennae very short. Antennules inserted inside fossae. Quadrangular buccal frame closed by third maxillipeds. Thoracic sternal sutures with deep obliquely transverse grooves ( Fig. 1 B). Chelipeds inflated, with smooth surface, sharp fingers. Ambulatory legs with articles cylindrical in cross-section; dactyli long, curved, sharp. Second pereopod subequal in length to cheliped.

Male abdomen with seven somites, including telson. First male gonopod almost straight, flattened apically ( Fig. 2 A–B).

Live specimen orange-red.

Etymology: The species is dedicated to Christian Fitialeata, a sailor of the R.V. Alis, a good man and esteemed colleague who suddenly passed away in Rabaul under unfortunate circumstances during the BIOPAPUA cruise.

Remarks: Oxypleurodon christiani n. sp. belongs to the Oxypleurodon group of species which has short flattened rostral spines ( Fig. 3 ). The other species in this group are O. auritum (Rathbun, 1916) , O. boholense Richer de Forges & Ng, 2009, and O. barazeri Richer de Forges & Ng, 2009.

Oxypleurodon christiani n. sp. is easily distinguishable from O. barazeri , where the carapace is more rounded with less marked dorsal plates less marked than in the new species ( Fig. 3 A versus Fig. 3 D) (Richer de Forges & Ng 2009: 252, fig. 3C). The main difference between O. christiani n. sp. and O. boholense is in the rostrum, which has sharp, diverging spines in O. boholense ( Fig. 3 C) (Ng et al. 2008: 107, fig. 88; Richer de Forges & Ng 2009: 252, fig. 3D) but rounded and clustered spines in O. christiani n. sp. ( Fig. 3 A). In O. christiani n. sp., the large cardiac plate is fused with the intestinal plate, forming a mushroom-shaped structure, in contrast to O. boholense where there are only a few marked intestinal plates ( Fig. 3 C). The long branchial plate is separated from the hepatic plate by a deep gap in O. boholense , whereas these two plates are completely fused in O. christiani n. sp. ( Fig. 1 C).

Oxypleurodon christiani n. sp. seems to be closest morphologically to O. auritum because the flattened rounded spines of the rostrum are similar ( Fig. 3 B) ( Griffin 1976: 211, fig. 10b; Takeda & Nagai 1979; Richer de Forges & Ng 2009: 252, fig. 3B). The differences, however, are obvious. In O. auritum , the carapace is pyriform, with a rounded branchial region ( Fig. 3 B) while the carapace is more triangular, with the branchial plate forming an acute angle in O. christiani n. sp. ( Fig. 1 A; 3A). The supraocular plate is also relatively larger in O. auritum than in O. christiani n. sp. ( Fig. 3 B versus Fig. 3 A). The mediogastric plate is oblong in O. christiani n. sp. ( Fig. 3 A) but posteriorly enlarged in O. auritum ( Fig. 3 B). The branchial and hepatic plates just touch each other in O. auritum whereas they are completely fused in O. christiani n. sp. Oxypleurodon christani n. sp. was first figured (but unnamed) on the color poster published by Tin-Yam Chan (National Taiwan Ocean University, Keelung) under the title " Papua New Guinea deep-sea crustaceans revealed by the survey of the BIOPAPUA cruise".

Figures

FIGURE 1. Oxypleurodon christiani n. sp. A, dorsal view; B, ventral view; C, lateral view of carapace (Photos by J. - F. Dejouannet).

FIGURE 2. Oxypleurodon christiani n. sp., holotype. A, first male gonopod; B, second male gonopod.

FIGURE 3. Comparative views of Oxypleurodon species. A, O. christiani n. sp. (Papua New Guinea, BIOPAPUA, stn. CP 3653); B, O. auritum (Philippines, AURORA, stn. CP 2678); C, O. boholense (Philippines, PANGLAO 2005, stn. CP 2362); D, O. barazeri (Solomon Is., SALOMON 1, stn. CP 1792). (Photographs: A-C, T. Y. Chan; D, J. - F. Dejouannet).