Paradynomene rotunda, Mclay, Colin L. & Ng, Peter K. L., 2004

Mclay, Colin L. & Ng, Peter K. L., 2004, A taxonomic revision of the genus Paradynomene Sakai, 1963 (Crustacea: Decapoda: Brachyura: Dynomenidae), Zootaxa 657, pp. 1-24 : 19-23

Paradynomene rotunda n. sp. ( Figs. 12 , 13 , 14 F)

Paradynomene tuberculata— McLay 1999: 543 (part).— McLay 2001: 820 . [Not Paradynomene tuberculata Sakai, 1963: 231 , fig 8.]

Material. Holotype female, 19.0 x 18.0 mm, station DW159, 52 m, 19°46.04'S, 158°19.09'E, Chesterfield Islands, coll. CORAIL 2, 1 Sep 1988 (MNHN­B26604). Others: 1 male, 22.7 x 21.3 mm, 1 female, 16.1 x 16.1 mm, northwest Luminao Reef, Guam, 13°27’N, 144°47’E, 21 m, among dead coral, coll. H. T. Conley, 29 May 1993 ( ZRC 2000.2122); 1 female, 8.6 x 8.8 mm, Luminao Reef, Guam, 21–24 m, among coral rubble, coll. H. T. Conley, 7 May 1998 ( ZRC 2000.750); 1 male, 21.7 x 20.0 mm, Piti Lagoon, Guam, 1.2–7.5 m, in dead coral, 26 May 1994 ( ZRC); 1 male, 17.2 x 16.4 mm, Piti Lagoon, Guam, 4–8 m, among dead coral, coll. 5 Jun 1994 ( ZRC); 1 ovigerous female, 20.5 x 19.4 mm, Piti Lagoon, Guam, 1.5–5 m, on coral rubble, coll. 12 May 1997 ( ZRC); 1 female, 14.8 x 13.9 mm, station TN2, gloomy submarine tunnels, "Tinian Grotto", Tinian, Mariana Islands, calcareous sand, depth 13–21 m, 15°01'06.3" N, 145°35'10.2"E, coll. Ohashi, Kinjo, Kano & Kase, 13 Nov 1997 (NSMT­Cr 15697).

Description. Carapace sub­oval, width slightly greater than length, anterior, posterior margins sub­parallel, lateral margins sub­circular. Surface areolate, areolae covered with small rounded granules, not closely packed, areas between areolae mostly smooth or only sparsely granulate. Carapace regions not well marked. Frontal groove shallow, separating pair of epigastric tubercles, followed by mesogastric area containing small median tubercle, with protogastric tubercle on each side. Pair of metagastric tubercles, similar in elevation to mesogastric tubercle, followed by pair of smaller urogastric tubercles. Cardiac area swollen, shallowly divided into 2 anterior tubercles. Intestinal tubercle absent. Branchial area dominated by 7 tubercles: 2 small epibranchial tubercles, 3 mesobranchial tubercles, 2 weakly separated tubercles, 1 near margin, 2 smaller metabranchial tubercles. Total of 23 areolate tubercles on whole carapace: 12 on each side, 1 unpaired median tubercle.

Rostrum bidentate, teeth small, followed by 2 small supraorbital tubercles, rest of orbital margin covered with small granules. Suborbital tubercle strong, subacute, visible dorsally. Orbits obliquely arranged, clearly exposed dorsally.

Anterolateral margin begins below level of postorbital corner armed with 6 sub­equal teeth, space between first and third may contain smaller tubercles. No hepatic teeth, first anterolateral tooth forms anterior corner of carapace. Behind branchial groove are 2 well developed posterolateral teeth, last forming posterior corner of carapace.

Pereopods covered in small granules as on carapace. Outer surface of cheliped carpus, propodus covered with small tubercles. Fingers straight, gaping, spoon­shaped, teeth well developed, 5 on fixed finger, 2 on moveable finger. At rest, fingers slot in beside bases of third maxillipeds that lack dense mass of fine setae. Margins of second to fourth pereopods tuberculate, fifth pereopod reduced, hidden under posterolateral carapace corner in dorsal view.

Surface of abdomen granulate, margins setose, especially around telson, abdomen only loosely held against sternum. No effective abdominal locking mechanism in mature female.

Etymology. From “rotundus”. Latin for round alluding to the more rounded carapace outline when compared to its congeners.

Remarks. The ovate carapace is very distinctive and easily distinguishes the species (see Table 1 ). The shape does not vary with size, the smallest specimens from Guam and the largest (the holotype from Chesterfield Islands) are all similarly shaped ( Fig. 12 ). Paradynomene rotunda is the only known shallow­water species of the genus, the depth range being 1– 52 m. The specimens from Guam were all obtained from coral rubble and collected using SCUBA. All the other species of Paradynomene are from deeper waters: P. tuberculata (85–402m), P. quasimodo (200–377m), P. t e u f e l (214–277m), P. diablo (360m), and P. demon (397m).

Figures

FIGURE 12. Dorsal views. A, Paradynomene rotunda n. sp., female holotype, 19.0 x 18.0 mm,, Chesterfield Islands (MNHN­B 26604); B, female, 8.6 x 8.8 mm, Guam (ZRC 2000.750).

FIGURE 13. Paradynomene rotunda n. sp., female holotype, 19.0 x 18.0 mm, Chesterfield Islands (MNHN­B 26604). A, schematic figure of carapace (small granules not drawn); B, schematic lateral view of carapace (small granules not drawn); C, gastric region of carapace showing pattern of granules and setae; D, outer view of right chela; E, dorsal view of right cheliped (small granules not drawn). Scales = 2.0 mm.

FIGURE 14. Frontal views. A, Paradynomene tuberculata Sakai, 1963, male, 21.5 x 22.3 mm, Loyalty Islands (MNHN­B 25249); B, P. quasimodo n. sp., holotype male, 14.3 x 15.4 mm, Philippine Islands (ZRC 2001.360); C, P. d emo n n. sp., holotype female, 23.2 x 24.0 mm,, New Caledonia (MNHN­B 26602); D, P. diablo n. sp., holotype male, 11.4 x 12.6 mm, Norfolk Ridge, New Caledonia (MNHN­B 26607); E, P. t e u f e l n. sp., holotype male 7.8 x 8.6 mm, Gulf of Aden (SMF); F, P. rotunda n. sp., holotype female, 19.0 x 18.0 mm, Chesterfield Islands (MNHN­B 26604).