Xenocrate, Ng, Peter K. L. & Castro, Peter, 2007

Ng, Peter K. L. & Castro, Peter, 2007, On a new genus and species of euryplacid crab (Crustacea: Decapoda: Brachyura: Goneplacoidea) from the Philippines, Zootaxa 1549, pp. 43-53 : 45

Xenocrate new genus

Diagnosis. Carapace subhexagonal; dorsal surface granular, regions poorly demarcated ( Fig. 1 AB); front lamellar, truncate, marked by distinct median notch ( Fig. 1 B); anterolateral margins with 2 teeth ( Fig. 1 A, B); basal antennal article short, closed by extension of carapace margin ( Fig. 1 C); posterior margin of epistome strongly lobulated ( Fig. 1 C); merus of third maxilliped auriculiform ( Fig. 2 A); no visible stridulating structures. Sterno-abdominal cavity of male reaching anterior margin of sternite 4 ( Figs. 2 B, 3A); press-button of abdomen-locking mechanism on anterior edge of thoracic sternite 5 ( Fig. 3 A); thoracic suture 2/3 deep; suture 3/4 shallow, medially interrupted; sutures 4/5, 6/7, 7/8 interrupted medially, 5/6 complete ( Figs. 2 B, 3A); male episternite 7 covering part of sternite 8 and coxa of P5; sternite 8 not visible when abdomen closed ( Fig. 2 C, D); penis coxo-sternal ( Fig. 3 C). Chelipeds relatively stout, long ( Fig. 1 A); P2–P5 long, slender; margins of dactylus and propodus setose. Male abdomen elongated, transversely narrow ( Fig. 2 B, C); somite 1 very narrow longitudinally, partially covered by posterior carapace margin ( Fig. 3 C, D). G1 very slender, with numerous denticles of varying sizes on distal half (Fig. 4A–C); G2 short, less than 1/3 G1 (Fig. 4D). Female abdomen relatively narrow, leaving distal portion of all thoracic sternites visible ( Fig. 5 B); vulva prominent but operculum absent ( Fig. 5 C).

Type species. Xenocrate peculiaris , new genus, new species, by monotypy.

Etymology. The name is derived from the Greek for strange, in arbitrary combination with the second syllable of Eucrate , which the new genus somewhat resembles. Gender feminine.

Remarks. Xenocrate new genus, is closest to Eucrate but differs in the markedly more hexagonal carapace, with the posterolateral margins gently convex (versus distinctly convex in Eucrate ); the dorsal carapace surface is prominently granular (versus smooth), the anterolateral margin has two sharp teeth (versus 3, rarely 4, lobes or relatively low teeth), the front is lamelliform and strongly projects anteriorly (versus low and truncate), the suborbital margin has a prominent median lamelliform rounded tooth (versus low lobe or entire), the anteroexternal angle of the merus of the third maxilliped is prominently auriculiform, expanding to partially cover the distal part of the exopod (versus angular but low, never covering any part of the exopod), the outer edges of the posterior margin of the epistome as well as the anterior part of the buccal cavity margin are prominently expanded and lamelliform (versus low), the cheliped is completely glabrous (versus chela and/or carpus with prominent tufts of soft setae), and the proportionately longer ambulatory legs, with the propodus and dactylus of the last pair (P5) laterally flattened, spatuliform and lined with dense setae (versus normal subcylindrical form with scattered and/or short setae). With regards to the carapace, although most species of Eucrate have three anterolateral teeth (rarely two), Xenocrate has only two such teeth.

Figures

FIGURE 1. Xenocrate peculiaris new genus, new species, holotype male, cl 34.0 mm, cw 39.1 mm (NMCR). A, overall view; B, dorsal view of carapace; C, frontal view of carapace.

FIGURE 2. Xenocrate peculiaris, new genus, new species, holotype male, cl 34.0 mm, cw 39.1 mm (NMCR). A, buccal cavity showing third maxillipeds; B, thoracic sternum and male abdomen; C, posterior part of thoracic sternum and first four abdominal somites; D, posterior carapace margin and first two abdominal somites.

FIGURE 3. Xenocrate peculiaris, new genus, new species, holotype male, cl 34.0 mm, cw 39.1 mm (NMCR). A, sternoabdominal cavity, showing position of press button of abdominal locking mechanism (indicated by arrows) and sternal sutures; B, position of penis, coxa of P 5 and episternite 7 (position of penis indicated by arrow); C, left chela. Abbreviations: BP = press button; St 7 = thoracic sternite 7; St 7 / 8 = sternal suture 7 / 8; Cox 4, 5 = coxa of P 4 and P 5 respectively; Pen = penis

FIGURE 5. Xenocrate peculiaris, new genus, new species, paratype female, cl 36.9 mm, cw 42.2 mm (ZRC). A, overall view; B, thoracic sternum and abdomen; C, sterno-abdominal cavity showing vulvae.