Diuplax, NG & Castro & Rodríguez Moreno, 2024

Ng, Peter K. L., Castro, Peter & Rodríguez Moreno, Paula A., 2024, Notes on the taxonomy of Frevillea A. Milne-Edwards, 1880 (Crustacea, Brachyura, Goneplacoidea), with the description of a new genus for F. sigsbei A. Milne-Edwards, 1880, Zoosystema 46 (29), pp. 733-748 : 741

Diuplax n. gen.

urn:lsid:zoobank.org:act:

TYPE SPECIES. — Frevillea sigsbei A. Milne-Edwards, 1880 , by present designation.

ETYMOLOGY. — The name is derived from the Latin diutius for “a long time,” in arbitrary combination with “- plax ”, the ending for many goneplacid taxa, alluding to the long time it took to discover the true generic affinities of F. sigsbei . The gender is feminine.

DIAGNOSIS. — Carapace broadly trapezoidal ( Fig. 5A, B, D, F, G ); anterolateral tooth adjacent to pronounced external orbital tooth, separated by deep cleft ( Figs 5A, B, D, F, G ; 6A, B ); posterior margin of epistome relatively wide transversely, margin almost straight ( Fig. 6A, B ); ocular peduncle relatively short, c. 2 times length of cornea ( Figs 5A, B, D, F, G ; 6A, B ); male thoracic sternites 1-4 relatively wide ( Fig. 5E ); male thoracic sternite 8 visible as triangular plate when pleon closed; pleonal somite 1 reaching coxa of fourth ambulatory leg; episternite 7 partially overlaps episternite 8 in ventral view, penis visible in oblique view, between narrow channel between episternites 7 and 8 ( Fig. 6 C-E); male pleon relatively narrower transversely, especially somites 3-6 ( Fig. 5E ); adult male cheliped short, relatively stout ( Fig. 5D, E ); fourth ambulatory dactylus spatuliform ( Fig. 5A, B, D ); G1 relatively short, broadly C-shaped, evenly distally tapering gradually to sharp tip, opening subdistal, large ( Fig. 6F, G ); G2 longer than G1; flagellum long, longer than basal article, distal part strongly recurved ( Fig. 6H, I ).

REMARKS

The differences between Diuplax n. gen. and Goneplax s. str. are pronounced (see Table 1 ). Secondary differences observed between Diuplax n. gen. and Goneplax s. str. that may be of generic value are: the cheliped merus of the former is short, stout, dorsal margin of merus possessing a low submedian tubercle ( Fig. 5B ) (elongated, slender, with a distinct short submedian spine on dorsal margin in Goneplax , Fig. 7F ); and the dorsal margin of the meri of the ambulatory legs have each show a subdistal angle but is not spiniform ( Fig. 5A, B, D ) (with a distinct subdistal spine in Goneplax s. str.; Fig. 7G ).

COMPARATIVE MATERIAL. — Goneplax rhomboides ( Linnaeus, 1758) • 3 ♂ (largest 36.5 × 22.6 mm); Kames Bay, Isle of Cumbray, Scotland; coll. S. De Grave; 2.VI.2005; ZRC 2010.0069 • 1♂ (22.0 × 35.8 mm); Grand Bassam, Abidjan, Ivory Coast, trawl; 250 m; coll. Le Loeuff & Intès; 23.XII.1966 (det. Goneplax angulata ) MNHN-IU-2024-5374 (= MNHN-B19812). Goneplax clevai Guinot & Castro, 2007 • 1♂ (21.3 × 35.3 mm); Port Elizabeth, South Africa; coll. S. Fennessy, from local trawlers; 1.XII.2003; ZRC 2004.0700.

Figures

FIG. 5. — Diuplax sigsbei (A. Milne-Edwards, 1880) n. comb.: A-C, lectotype ovigerous ♀ (15.3 × 9.5 mm) (MCZ-IZ-CRU-10991); D, E, paralectotype ♂ (14.1 × 8.4 mm) (MCZ-IZ-CRU-10992); F, ♂ (13.0 × 8.5 mm) (MNHN-IU-2014-11828); G, ♀ (10.8 × 7.3 mm) (MNHN-IU-2014-11828): A, B, D, F, G, overall dorsal view; C, E, ventral view of cephalothorax and pleon. Credits: A, after A. Milne-Edwards & Bouvier (1923: pl. 6, fig. 2); B, C, photographs by Alana Rivera, MCZ; D-G, pho- tographs by P. K. L. Ng.

FIG. 6. — Diuplax sigsbei (A. Milne-Edwards, 1880) n. comb.: A, lectotype ovigerous ♀ (15.3 × 9.5 mm) (MCZ-IZ-CRU-10991); B-I, ♂ (13.0 × 8.5 mm) (MNHN- IU-2014-11828); A, frontal view of cephalothorax;B, left side of carapace showing orbit and third maxilliped (left side);C, ♂ thoracic sternite 8 and pleonal somites 1 and 2; D, sternopleonal cavity; E, penis and coxa of fourth ambulatory leg (tilted at angle to see penis); F, left G1; G, distal part of left G1; H, left G2; I, distal part of left G2. Credits: A, after A. Milne-Edwards & Bouvier (1923: fig. 3); B, D, F-I, after Guinot (1969b: figs 63, 68, 71, 72); C, E, by P. K. L. Ng. Abbreviations: cx5, coxa of fourth ambulatory leg; pe, penis; so1, 2, pleonal somites 1 and 2, respectively; st5-8, thoracic sternites 5-8.

FIG. 7. — Goneplax rhomboides (Linnaeus, 1758), ♂ (36.5 × 22.6 mm) (ZRC 2010.0069), Scotland. A, dorsal view of carapace; B, frontal view of cephalothorax; C, left third maxilliped; D, anterior thoracic sternum and pleon; E, posterior thoracic sternum and pleon; F, right merus of cheliped (inner view); G, left fourth ambulatory leg. Credits: photographs by P. K. L. Ng.