Paradynomene Sakai, 1963

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 : 2-3

Paradynomene Sakai, 1963

Paradynomene Sakai, 1963: 230 .— McLay, 1999: 542.

Diagnosis. Carapace sub­rectangular or sub­oval, surface markedly convex, areolate, regions distinct. Lateral carapace margins not well defined, sub­parallel or slightly convex, armed with irregular teeth. Frontal margin truncate, rostrum bi­ or tridentate. Eyes protected by well defined orbits, exposed dorsally. Sternal sutures 7 and 8 of female end well apart on low tubercles behind bases of third pereopods. Body sparsely setose except along margins of abdomen, which can be fringed with setae. Antennule may be concealed inside orbit at base of eyestalk. First article large, triangular, filling large part of ventral orbital region. Antennal flagella shorter than half of carapace width. All articles of antenna moveable, first segment (urinal) beaked medially. Third maxillipeds opercular, sharply angled, completely covering buccal cavern, separated at bases by sternite, basis, and ischium of endopod fused but always marked by shallow suture. Crista dentata with 12–14 small teeth increasing in size distally, first five or six may be obsolete. Chelipeds robust, equal, stouter than ambulatory legs, last pair of legs very reduced, dactyl rudimentary, forming obsolete chelate mechanism with extension of propodus only in female. Branchial formula 19 gills + 7 epipods (for detailed branchial formula see McLay, 1999: 546). Abdomen of six segments and telson, folded loosely under thorax, uropods large, abdominal locking mechanism not functional. Both sexes with five pairs of pleopods, first pair rudimentary in female, last three pairs vestigial in male. First pair of male pleopods stout, setose semirolled tube with apical plate, second pair needle­like with linear row of tiny inset spines along anterior surface.

Type species. Paradynomene tuberculata Sakai, 1963 , by monotypy (gender feminine).

Included species. Paradynomene tuberculata Sakai, 1963 , P. quasimodo n. sp., P. demon n. sp., P. diablo n. sp., P. t e u f e l n. sp., and P. ro t u n d a n. sp.

Terminology. A feature of the species of Paradynomene is the granular surface of the carapace and the presence of areolae that may be tipped by a distinct group of granules. These areolae range from slightly swollen areas not greatly elevated, to steep­sided, volcano­like mounds, tipped with a distinct group of granules. We have used the term "tubercle" to refer to those areolae that are clearly peaked with the highest elevation being marked by a group of granules. On the figures, these tubercles are marked by small circles. Thus for some species the number of swollen areas on the carapace may be greater than the given number of tubercles. We have used the terms "gastric", "cardiac", "branchial," and 'intestinal" as used by Rathbun (1930) in describing the location of these tubercles ( Fig. 1 ). Another character that requires careful attention is the number of anterolateral teeth. The problem arises because the anterolateral margins are not well­defined and projections on, or placed higher, but overhanging the margin, are variable in size and sometimes the left side can differ from the right. A distinction needs to be made between teeth, which are granulated projections on the anterolateral margin, and granules, which are smaller and form part of the background carapace ornamentation. The number of teeth that are given in the text include only the maximum number of distinct projections and do not include the smaller granules. Posterolateral teeth are those on the margin posterior to the maximum carapace width. The terminology otherwise follows that of McLay (1999).

Remarks. The genus Paradynomene was erected by Sakai (1963) for an unusual male dynomenid crab collected from Sagami Bay at 85 m. Instead of being transversely oval or polygonal and slightly convex, like species of Dynomene Desmarest, 1823 , this crab was subquadrangular and markedly convex with tuberculate areolae, and the "face" more closely resembled dromiids belonging to Epigodromia McLay, 1993 . Sakai (1976) subsequently reported on a second specimen (a female) from Japan. For many years they were the only known specimens. In his revision of the Dynomenidae, McLay (1999) assembled a collection of 19 specimens from New Caledonia (including the Norfolk Ridge), Chesterfield and Loyalty islands, Indonesia, Guam, and the Gulf of Aden, all of which were referred to P. tuberculata . McLay (2001) subsequently recorded further specimens from Guam. Many of the locations were represented by only a few specimens, often small, making precise species determinations difficult. The recent specimens from the Philippines facilitated a reassessment of the species definitions and allowed us to establish a narrower concept of P. tuberculata and to argue that the genus Paradynomene should not be regarded as monotypic. This revision means that six species are now recognized, five of which are new. Of the specimens studied by McLay (1999), only a few can be referred to P. tuberculata s. str.

Figures

FIGURE 1. Carapace of Paradynomene showing major regions and the terminology used in the text.