Villoplax peruvianus ( Garth, 1973 )

CASTRO, PETER & NG, PETER K. L., 2010, Revision of the family Euryplacidae Stimpson, 1871 (Crustacea: Decapoda: Brachyura: Goneplacoidea), Zootaxa 2375 (1), pp. 1-130 : 113-115

Villoplax peruvianus ( Garth, 1973) , new combination

( Figs. 47A–D ; 48A–G )

Goneplax sp. — Chirichigno 1970: 61, fig. 150.

Trizocarcinus peruvianus Garth, 1973: 9 , fig. 5 [ Perú]. — Wicksten 1989: 303 [in list], 316 [in list]. — Ng et al. 2008: 78 [in list].

Type material. Pre-adult female holotype, 13.4 mm × 19.1 mm ( AHF 699 , now LACM) ( Fig. 47A, B ); 1 male paratype, 19.9 mm × 28.7 mm ( AHF 705 ; now LACM) ( Fig. 47C, D ) .

Type locality. Perú, off Paita , 144 m.

Material examined. Perú. Off Paita , stn. 106, 144 m, E. N. del Solar coll.: 1 male paratype, 19.9 mm × 28.7 mm ( AHF 705 , now LACM), pre-adult female holotype, 13.4 mm × 19.1 mm ( AHF 699 , now LACM) .

Diagnosis. Carapace with one short, acute tooth on each anterolateral border ( Figs. 47A, B ; 48A ). Ambulatory legs with long, conspicuous tomentum ( Fig. 48A ).

Remarks. The holotype, regarded as a female by Garth (1973) is actually a pre-adult specimen where the vulvae are barely visible and closed.

Distribution. Only known from northern Perú, Tropical Eastern Pacific region. Depth: subtidal to at least 144 m.

Genus Xenocrate Ng & Castro, 2007

Xenocrate Ng & Castro, 2007: 45 . — Ng et al. 2008: 78 [in list]. — De Grave et al. 2009: 33 [in list].

Diagnosis. Carapace ( Fig. 49A ) subhexagonal, almost as wide as long, dorsal surface granular without clear indication of regions; anterolateral borders arched; front wide, nearly straight with median notch, transverse sulcus along margin. Two short teeth (second acute, dorsally salient; small third tooth in small individuals) posterior to short, rounded outer orbital angle. Orbits ( Fig. 49C ) short, shorter than front, wide, spherical; 2 notches, large, thick inner suborbital tooth, shorter, thick median tooth, outer notch on thick suborbital border ( Fig. 49B, C ); eye peduncles short, about as long as cornea ( Fig. 49C ); large, spherical corneas. Basal antennal article immobile, orbital hiatus is closed excluding antennal flagellum from orbit ( Fig. 49B, C ). Anteroexternal margin of third maxilliped merus auriculiform ( Fig. 49B ). Cheliped fingers ( Fig. 49D ) moderately stout, slightly longer than swollen propodus, dark in colour; carpus with tooth on inner margin; glabrous. Dorsal margins of ambulatory legs (P2–P5) meri, carpi, propodi unarmed, dactyli slender, smooth, setose; P5 propodus, dactylus proportionally short, flattened, fringed with many short setae ( Fig. 49A ). Thoracic sternum ( Fig. 49G, H ) wide; thoracic suture 2/3 complete, straight ( Fig. 49G ); 3/4 deep, short, interrupted; 3/4 deep, short, interrupted; 4/5, 6/7, 7/8 interrupted, 5/6 complete ( Fig. 49G, H ); median groove on thoracic sternites 7, 8. Sterno-abdominal cavity of male deep, nearly reaching anterior margin of sternite 4 ( Fig. 49G ). Press-button of male abdominal-locking mechanism as large tubercle near thoracic suture 4/5 ( Fig. 49G ) (presence in preadult females unknown). Male abdomen narrow, slender (T-shaped), lateral margins of somites 4–6 abruptly narrowing from somite 3 to transversely narrow, pointed telson ( Fig. 49E ); somite 3 transversely reaching inner margins of P5 coxae; no portions of thoracic 8 exposed by closed abdomen, somite 2 transversely shorter than somite 3 ( Fig. 49F ). G1 long, slender, slightly sinuous, acuminate apex, with small denticles ( Fig. 50A–C ); G2 less than one-third of G1, apex flattened, with obtuse tip ( Fig. 50D ). Male genital opening (gonopore) coxal; coxo-sternal disposition of long penis, protected by concave posterior portion of thoracic sternite 7 ( Ng & Castro 2007: fig. 3B). Female abdomen relatively narrow, not covering outer portions of thoracic sternum ( Ng & Castro 2007: fig. 5B). Vulva ovoid, with thick borders, extending across anterior portion of sternite 6 close to median axis of thorax ( Fig. 49H ); covered by soft membrane, sternal vulvar cover absent. Remarks. This monotypic genus was recently described from specimens collected in the Philippines ( Ng & Castro 2007: 45, figs. 1–5). It is herein reported for the first time from the Solomon Is. and Vanuatu, which suggests a more extensive geographical distribution.

The G2 has a unique flattened apex with an obtuse tip instead of the two unequal processes characteristic of most euryplacids, with the basal, much shorter process missing ( Fig. 50D ). Other characters of Xenocrate are summarized in Table 1.

Species included. Xenocrate peculiaris Ng & Castro, 2007 The genus is restricted to the Indo-West Pacific region.

Figures

FIGURE 47. Villoplax peruvianus (Garth, 1973); A, B, female holotype of Trizocarcinus peruvianus Garth, 1973 (13.1 mm × 19.1 mm) (AHF 699; now LACM); C, D, male paratype of Trizocarcinus peruvianus Garth, 1973 (19.9 mm × 28.7 mm) (AHF 705; now LACM); Perú, off Paita. A, overall view; B, dorsal view of carapace; C, frontal view showing orbits and antennae; D, ventral view of carapace. Abbreviations: a3 = male abdominal somite 3; es7 = episternite 7; s4– s7 = thoracic sternites 4 to 7, respectively; t = telson. Photo credits: J. Martin (LACM).

FIGURE 48. Villoplax peruvianus (Garth, 1973); male paratype of Trizocarcinus peruvianus Garth, 1973 (10.0 mm × 28.9 mm) (LACM), Perú, off Paita. A, overall view; B, frontal view showing third maxillipeds, orbits, and antennae; C, outer surface of right chela; D, male abdomen; E, F, G1; G, G2 (after Garth 1973: fig. 5). Abbreviations: a2, a3 = male abdominal somites 2 and 3, respectively.

FIGURE 49. Xenocrate peculiaris Ng & Castro, 2007; A–G, male holotype (34.0 mm × 39.1 mm) (NMCR), Philippines, Bohol; H, female paratype (36.9 mm × 42.2 mm) (ZRC 2008.0427), Philippines, Bohol. A, overall view; B, third maxillipeds; C, frontal view showing orbits and antennae; D, outer surface of left chelae; E, anterior portion of male thoracic sternum and abdomen; F, posterior portion of male thoracic sternum and abdomen; G, male sterno-abdominal cavity and G1; H, female thoracic sternum and vulvae. Abbreviations: a1–a3 = male abdominal somites 1, 2, 3, respectively; cx5 = coxa of fifth pereopod (P5); G1 = first male pleopod; mg = median groove; pb = press-button of male abdominal-locking mechanism; s4–s7 = thoracic sternites 4 to 7, respectively; v = vulva.

FIGURE 50. Xenocrate peculiaris Ng & Castro, 2007; male holotype (34.0 mm × 39.1 mm) (NMCR). A–C, G1; D, G2 (after Ng & Castro 2007: fig. 4). Scale bars: 1.0 mm.