Oxypleurodon wilsoni, Forges & Poore, 2008

Forges, Bertrand Richer de & Poore, Gary C. B., 2008, Deep-sea majoid crabs of the genera Oxypleurodon and Rochinia (Crustacea: Decapoda: Brachyura: Epialtidae) mostly from the continental margin of Western Australia, Memoirs of Museum Victoria 65, pp. 63-70 : 64

Oxypleurodon wilsoni sp. nov.

Figure 1b

Rochinia aff. luzonica .— Poore et al., 2008: 56 (colour fig.).

Material examined. Holotype: Australia. WA. Off Two Rocks (31°36.32'S – 31°37.02'S, 114°58.52'E –114° 58 16'E), 329–370 m, 19 Nov 2005 (stn SS10/2005 006), WAM C400529 (ovigerous female 15.7 x 15.4 mm).

Paratypes. Collected with holotype, WAM C400530 (ovigerous female, 16.4 x 14.0 mm). WA. Off Abrolhos (29°00.46'S – 29°01.23'S, 113°46.44'E – 113°47.06'E), 419–439 m, 03 Dec 2005 (stn SS10/2005 088), NMV J54070 (male, 18.5 x 19.6 mm). Off Two Rocks (31°37.05'S – 31°37.23'S, 114°58.19'E – 115°14.39'E), 364–404 m, 19 Nov 2005 (stn SS10/2005 004), NMV J54069 (3 males, 14.4 x 13.5 mm, 13.9 x 13.4 mm, 9.6 x 8.8 mm) .

Diagnosis. Carapace to 18.5 mm, long, pyriform. Carapace, including pseudorostral spines, covered with short setae. Carapace bearing several elevated plates and tubercles arranged as follows: 1 cardiac plate, round and forming a conical point in its middle; 2 branchial plates, thin, sharp and pointing laterally; 2 epibranchial plates, thin, sharp and oriented obliquely; 1 ovoid mesogastric plate; 2 hepatic plates touching the postocular plates forming together a L-shape; 1 small subbranchial oblong plate on the lateral border; 2 supraocular plates, sharp anteriorly; 1 anterogastric tubercle; 1 tubercle on each side of mesogastric plate; posterior border of the carapace thick, forming medially a large tooth pointing backward. Pseudorostral spines long and sharp, diverging in a V. Eyes small, completely inserted in the orbits, the postocular plate forming a cup. Basal antennal article fused with carapace. Cheliped shorter than pereopod 2. Articles of ambulatory legs cylindrical. Female abdomen of 7 segments.

Distribution. South-western WA slope (29°– 31.5°S), 329–439 m depth.

Etymology. Dedicated to Dr Robin Wilson in recognition of his enthusiasm and hard work during the cruise when this species was collected, and at all times.

Remarks. Oxypleurodon wilsoni sp. nov. belongs in the group of species of Oxypleurodon having long and sharp branchial plates: O. luzonicum ( Rathbun, 1916) , O. stuckiae ( Guinot and Richer de Forges, 1986b) , O. karubar Richer de Forges, 1995 , and O. lowryi ( Richer de Forges, 1992) .

In O. wilsoni the supraocular plate is sharp anteriorly whereas it is rounded in O. luzonicum . The cardiac plate is small, round and elevated in the middle (round and flat in O. luzonicum ). The epibranchial plates are oblong, pointing externally in O. wilsoni but small and triangular in O. luzonicum . The mesogastric plate is ovoid but lozenge-shaped in O. luzonicum . Between the mesogastric spine and the hepatic spine lies a small tubercle absent in O. luzonicum .

O. wilsoni is distinguishable from O. stuckiae by the presence of a supraocular spine. The pseudorostral spines are longer and less diverging in O. wilsoni than in O. stuckiae . An anterior gastric tubercle in O. wilsoni is not seen in O. stuckiae .

O. wilsoni differs from O. karubar in the following characters: the epibranchial plate is straight but curved in O. karubar ; the pseudorostral spines are straight but enlarged basally in O. karubar ; the anterior part of the supraocular plate is spiniform in O. wilsoni but rounded in O. karubar ; the hepatic plate touches the postocular plate forming together an L-shape in O. wilsoni but these are several disjointed pieces in O. karubar .

The shape of the carapace is pyriform in O. wilsoni while it is large and rounded posteriorly in O. lowryi . The supraocular plate points forward in O. wilsoni but laterally in O. lowryi . The branchial spines are straight in O. wilsoni while they are curved in O. lowryi .

The ambulatory legs of the holotype and paratype from the same sample are mixed and it is not possible to be precise about the relative lengths of pereopods.

The species was collected over narrow latitudinal and depth ranges.

Figures

Figure 1. Lateral and dorsal views, scale = 5 mm. a, Oxypleurodon luzonicum (female,NMV J58221).b, Oxypleurodon wilsoni sp. nov. (holotype, WAM C400259). c, Rochinia annae sp. nov. (holotype, WAM C400531). d, Rochinia carinata (male, NMV J53872).