Gecarcoidea H. Milne Edwards, 1837

Guinot, Danièle, Ng, Ngan Kee & Rodríguez Moreno, Paula A., 2018, Review of grapsoid families for the establishment of a new family for Leptograpsodes Montgomery, 1931, and a new genus of Gecarcinidae H. Milne Edwards, 1837 (Crustacea, Decapoda, Brachyura, Grapsoidea MacLeay, 1838), Zoosystema 40 (26), pp. 547-604 : 569

Genus Gecarcoidea H. Milne Edwards, 1837

TYPE SPECIES. — Gecarcoidea lalandii H. Milne Edwards, 1837 (see N. K. Ng et al. in press) by monotypy.

OTHER SPECIES. — Gecarcoidea humei (Wood-Mason, 1874) ; G. natalis (Pocock, 1889) (see Lai et al. 2017). All from the Indo-West Pacific.

DIAGNOSIS

Proepistome as small plate inserted under the lower frontal margin ( Fig. 7H ) ( Tavares 1989: fig. 7); male gonopore emerging far from P5 coxo-sternal condyle ( Fig. 7G ); thoracic sternum ( Fig. 7 E-G) with sternite 1 as very small, narrow tooth, not separated by suture from sternite 2; sternite 2 developed, semi-ovate; suture 2/3 V-shaped; no suture 3/4, no lateral trace; completely fused sternites 3+ 4 with straight, obliquely directed lateral margins, thus not restricted at level of P1; sternite 8 not developed medially, the triangular posterior emargination reaching sternite 7 at level of thick median bridge at level of suture 7/8; suture 7/8 short; median line only on sternite 7, with its distal part bumping at level of suture 6/7 into weak median bridge that superficially units both sides of the sternal plate and becomes the bottom of the sterno-pleonal cavity ( Fig. 7F, G ); no portion of sternite 8 dorsally exposed when pleon is folded; locking button as large prominence occupying half proximal part of sternite 5, close to suture 4/5 ( Fig. 7F ), surrounded by setae (no delineated pleonal socket); on sternite 4 a thickened region forming hook-like edge close to suture 4/5 ( Fig. 7F ), resembling a clasping apparatus or safety catch, however apparently not functional (described by Guinot 1979: 153, as “cran d’arrêt” in some Uca sensu lato, and later recognised as a key innovation for the recognition of several distinctive genera within Uca sensu lato, see Beinlich & Hagen 2006: fig. 3b, c; Köhnk et al. 2017: fig. 19e). Numerous oblique rows of tubercles covering subhepatic region, but no known report in the emission of stridulation Pterygostomial region glabrous, as in Gecarcinus and Johngarthia . Dense tufts of hydrophilic setae located along margins of pleon and at its junction with carapace in Gecarcoidea ( Fig. 7 E-G), G. natalis and G. lateralis having setal tufts extending along first three pleonal segments and on e P5 coxae, such as in Gecarcinus ( Fig. 7 A-C) and Johngarthia .

Figures

FIG. 7. —Thoracic sternum and frontal view: A-D, Gecarcinus ruricola (Linnaeus, 1758), ♂ 55.0× 76.0 mm, Cuba, MNHN-IU-2017-8392 (= MNHN-B13155); E-H, Gecarcoidea lalandii H. Milne Edwards, 1837, ♂ 52.0 × 73.3 mm, Papua New Guinea, MNHN-IU-2013-13254: A, E: thoracic sternum (brushed) with pleon; B, F, thoracic sternum (brushed) without pleon; C, G: genital region with gonopore and penis, D, H, front, proepistome, cephalic appendages, orbit and mxp3. Scale bars: 10 mm.