Thursday, November 30, 2017

[Crustacea • 2017] Pleistacantha kannu • A New Large Oregoniid Spider Crab of the Genus Pleistacantha Miers, 1879 (Brachyura, Majoidea), from the Bay of Bengal, India


Pleistacantha kannu
 Ng, Ravinesh & Ravichandran, 2017


Abstract
A new species of deep-water oregoniid spider crab of the genus Pleistacantha Miers, 1879, is described from the Indian Ocean. The species is distinct in possessing a prominently inflated carapace in which the median parts of the branchial regions almost meet. It can also be distinguished from its closest congeners, P. moseleyi (Miers, 1885), P. pungens (Wood-Mason, in Wood-Mason and Alcock 1891), and P. ori Ahyong & Ng, 2007, in its more elongate and less spinose chelipeds and ambulatory legs, shorter third maxilliped, trapezoidal male pleon and a male first gonopod which is relatively stout with a short subdistal dorsal papilla.

Keywords: deep-water, Indian Ocean, new species, Oregoniidae, Pleistacantha, taxonomy


Figure 1. Pleistacantha kannu sp. n., colour in life. A holotype male (cl 106.2 mm, cw 87.0 mm) (CASAU), India B paratype ovigerous female (cl 84.4 mm, cw 71.5 mm) (CASAU), India. 

Systematics

Family Oregoniidae Garth, 1958
Genus Pleistacantha Miers, 1879

Type species: Pleistacantha sanctijohannis Miers, 1879, by original designation.

Pleistacantha kannu sp. n.
?Pleistacantha adenicus Kazmi 1997  (nomen nudum).

Diagnosis: Carapace broadly pyriform, postrostral carapace length equal to or slightly longer than carapace width (ratio 1.0–1.1) (Figs 2A, B, 4C, D); dorsal carapace surface with short spines with relatively wider bases (Figs 2A, B, 4C, D, 5C, D); gastric regions strongly swollen (Figs 2A, B, 4C, D, 5C, D); branchial regions strongly swollen laterally and dorsally; medially separated by narrow space, area without spines, spines on margins of regions overlapping (Figs 2A, B, 4C, D, 5C, D); posterior carapace margin convex (Fig. 4C); rostrum relatively short; gently divergent, directly obliquely laterally, not curving upwards (Figs 2A, B, 4C, D, 5C, D, 6E); interantennular spine short, tip bifurcated with shallow concavity between short processes (Figs 6E, F); lateral margins of posterior margin of epistome strongly concave (Fig. 7G, H); ischium of third maxilliped short (Fig. 7I); adult male cheliped elongate, merus and chela slender (Figs 2A, 8F); surface of adult male chela mostly smooth, proximal part with short tubercles or granules, without long spines (Figs 2A, 8E, F); male anterior thoracic sternum relatively broad; surface with numerous blunt and sharp tubercles, never spines (Fig. 9E); male pleon transversely wide; distinctly trapezoidal; surface with numerous blunt and sharp tubercles, never spines (Fig. 9F); G1 relatively stout; distal part gently curved; subdistal dorsal papilla short (Fig. 10K–M).


Etymology: Name after the late Professor T. Kannupandi, an influential crustacean worker from the Centre of Advanced Study in Marine Biology in Annamalai University. The name, a shortened version of his family name, is used as a noun in apposition.


 Peter K. L. Ng, Raveendhiran Ravinesh and S. Ravichandran. 2017. A New Large Oregoniid Spider Crab of the Genus Pleistacantha Miers, 1879, from the Bay of Bengal, India (Crustacea, Brachyura, Majoidea). ZooKeys. 716: 127-146.  DOI: 10.3897/zookeys.716.21349

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