Pedroplax megalops ( Takeda, 1989 ) Takeda, 1989

Ng, Peter K. L. & Komai, Tomoyuki, 2011, A new genus for Psopheticus megalops Takeda, 1989 (Crustacea: Brachyura: Goneplacidae), Zootaxa 2934, pp. 61-67 : 62-63

publication ID	https://doi.org/ 10.5281/zenodo.203270
DOI	https://doi.org/10.5281/zenodo.6194161
persistent identifier	https://treatment.plazi.org/id/5240BA10-9762-FFC5-4DDB-FA3EFADB27ED
treatment provided by	Plazi
scientific name	Pedroplax megalops ( Takeda, 1989 )
status	comb. nov.

Treatment

Pedroplax megalops ( Takeda, 1989) View in CoL new combination

( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Psopheticus megalops Takeda, 1989: 172 View in CoL , figs. 16, 17; Castro 2007: 738, 739. Psopheticus megalops View in CoL —Ng et al. 2008: 80.

Material examined. Holotype: male (5.6× 4.8 mm) (NSMT-Cr 9754), Oshima Passage, 25–40 m depth, coll. Kagoshima University, 29 June 1970. Paratype: female (5.1× 4.4 mm) (NSMT-Cr 5297), east of Tanegashima, ca. 59 m depth, coll. M. Takeda & M. Imajima, 18 June 1975. Others: 1 male (5.2× 4.4 mm) (CBM-ZC5936), south of Amuro Island, Kerama Group, Ryukyu Islands, 2610.00’N, 12718.90’E, 52 m, dredge, station 7, coll. T. Komai, TRV Toyoshio-maru, 1998-4 cruise, 19 May 1998; 2 ovigerous females (4.2× 3.7 mm, 4.4×4.0 mm) (CBM-ZC 7623), north of Yakabi Island, Kerama Group, Ryukyu Islands, 55–101 m, 2615.34’N, 12715.98’E, dredge, station E-6, coll. T. Komai, RV Tansei-maru, KT02-3 cruise, 19 April 2002; 1 ovigerous female (3.9× 3.5 mm) ( ZRC 2011.0203), off Nagannu Island, Okinawa Islands, 2614.64’N, 12731.01’E, 51 m, dredge, coll. TRV Toyoshiomaru, 2005 cruise, 22 May 2005.

Description of male. Carapace quadrate, longer than broad, 1.1–1.2 times broader than long ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 A). Dorsal surface glabrous, almost smooth but with numerous minute low granules; granules relatively more prominent along frontal, anterolateral margins; H-shaped gastro-cardiac groove deep ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 A). Front entire, median part gently concave, short sulcus separating it from low lateral lobe ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, 3A). Orbit short, ovate; eyes relatively large, mobile, cornea large, protruding beyond outer margin of orbit, ocular peduncle very short, distal part with numerous small granules ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, 3A). Supraorbital margin entire, no trace of external orbital angle or tooth ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, 3A). Suborbital margin sinuous, entire, resembling rim around eye, with low inner sublobiform tooth ( Fig. 2 View FIGURE 2 A, C). Anterolateral margin very short, gently concave, lateral tooth prominent but not sharp, sublobiform, gently curving obliquely anteriorly, upwards ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 A, 3A). Posterolateral margins gently converging towards posterior carapace margin; region just behind anterior part of posterolateral margin gently swollen, with low rounded crest posteriorly ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 B, 3A). Posterior carapace margin gently concave ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 B, 3A). Hepatic, ptergostomial, subhepatic regions appear smooth but covered with numerous minute low granules ( Fig. 2 View FIGURE 2 A). Antennule relatively large, fossa asymmetrical with outer margin longer than inner, distal segments folding transversely ( Fig. 2 View FIGURE 2 A). Basal antennal segment mobile, rectangular; flagellum relatively short, as long as width of orbit, lodged inside orbit ( Fig. 2 View FIGURE 2 A). Epistome relatively broad, anterior part triangular; posterior margin sinuous with 3 low median lobes, separated from lateral parts by deep concavity ( Fig. 2 View FIGURE 2 A). Endostomial ridges well developed. Third maxillipeds subquadrate, forming small basal gape medially when closed, gets wider anteriorly; merus about as long as wide, anterolateral angle rounded, not auriculiform; ischium subrectangular, very shallow, barely discernible sulcus. Exopod slender, reaching anterior margin of merus, with prominent tooth on inner subdistal margin; flagellum long ( Figs. 2 View FIGURE 2 C, 3B).

Chelipeds homochelous, asymmetrical; surfaces almost glabrous, smooth ( Fig. 1 View FIGURE 1 , 3 View FIGURE 3 C, D). Merus short, with low rounded tooth on subproximal dorsal margin, margins gently granular ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 C). Carpus with large, obtuse lobiform tooth on inner angle ( Figs. 1 View FIGURE 1 , 3 View FIGURE 3 C, D). Chela stout, fingers laterally flattened, longer than palm, cutting edges with uneven cutting teeth ( Fig. 3 View FIGURE 3 D).

Ambulatory legs slender, articles smooth, with scattered plumose, simple setae; second leg longest ( Fig. 1 View FIGURE 1 ). Meri slender, dorsal margins gently serrated, without trace of distal or subdistal angle ( Figs. 1 View FIGURE 1 B, C, 3E). Propodi laterally flattened with median sulcus, that of fourth leg ovate, subfoliaceous ( Figs. 1 View FIGURE 1 B, C, 3E). Dactyli slender, covered with very short setae but not obscuring surface, gradually tapering to distal part, gently curved distally; that of fourth leg laterally flattened, subspatuliform, broadest medially ( Fig. 1 View FIGURE 1 B, C).

Surface of thoracic sternites covered with low, small granules, appearing almost smooth. Sternites 1, 2 completely fused, forming prominent triangular plate, separated from sternite 3 by shallow but distinct suture ( Figs. 2 View FIGURE 2 C, D). Sternites 3, 4 completely fused except for lateral sutures; sutures between sternites 4–8 medially interrupted; longitudinal groove present between sternites 6–8. Press button of abdominal locking mechanism present as prominent, rounded tubercle on anterior half of sternite 5 ( Figs. 2 View FIGURE 2 D). Penis coxal, opening to base of G1 through narrow channel formed by episternite 7, sternite 8 ( Fig. 2 View FIGURE 2 E).

Sterno-abdominal cavity relatively broad; male abdomen reaching to level between posterior edges of coxae of chelipeds ( Fig. 2 View FIGURE 2 C, D). Abdomen relatively broad, broadly T-shaped, all somites, telson free. Somite 1 longitudinally narrow, reaching to bases of coxae of last ambulatory legs; somite 2 almost twice height of somite 1, not reaching base of legs, large part of sternite 8 exposed; somite 3 transversely trapezoidal, almost reaching coxae of last ambulatory legs except for narrow part of sternite 8 ( Figs. 2 View FIGURE 2 B, 3G); somites 4, 5 trapezoidal; somite 6 rectangular, lateral margins almost parallel ( Fig. 2 View FIGURE 2 C, 3F); telson triangular with strongly convex lateral margins, rounded tip ( Figs. 2 View FIGURE 2 C, 3F).

G1 relatively stout, gently curved outwards, distal quarter tapering to sharp tip, with 2 stout subdistal spines on outer margin ( Fig. 3 View FIGURE 3 H, I). G2 slender about 1.3 times length of G1, median part dilated with numerous short spines on outer margin, distal part elongated, tip bifurcated with 4 or 5 subdistal spines ( Fig. 3 View FIGURE 3 J, K).

Female characters. The female chelae are similar to that of the males in form but weaker and relatively more slender. The abdomen is rounded, covering the entire thoracic sternum with all the somites free. The telson is broadly triangular with lateral margins gently sinuous but not contiguous with the margins of somite 6. There is no visible abdominal locking press-button structure. The vulvae are prominent, occupying most of anterior half of sternite 6, without visible sternal vulvar cover ( Fig. 2 View FIGURE 2 F).

Remarks. There are a surprisingly small number of eggs for the three ovigerous females examined. The two larger females (4.2× 3.7 mm and 4.4×4.0 mm, CBM-ZC7623) had 15 and 24 eggs respectively, while the smaller female (3.9× 3.5 mm, ZRC 2011.0203) had 25 eggs. The relatively large size (ca. 0.5–0.6 mm in diameter), especially in relation to the small size of the female, and small number of eggs suggest the larvae may be partially or perhaps even fully abbreviated (e.g., see Tan et al. 1986).

Pedroplax megalops is so far known only from southern Japan. It has been dredged from depths of 25 to 101 m.