Crocydocinus, Lee & Forges & Ng, 2019

Lee, Bee Yan, Forges, Bertrand Richer De & Ng, Peter K. L., 2019, Deep-sea spider crabs of the family Epialtidae MacLeay, 1838, from Papua New Guinea, with a redefinition of Tunepugettia Ng, Komai & Sato, 2017, and descriptions of two new genera (Crustacea: Decapoda: Brachyura: Majoidea), Zootaxa 4619 (1), pp. 1-44 : 23-25

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n. gen.

Genus Crocydocinus n. gen.

Type species. Crocydocinus ewok n. sp., by present designation, gender masculine.

Diagnosis. Carapace pyriform. Carapace region well-defined. Pseudorostral spines short, bifid. Carapace, legs covered in thick layer of setae. Antennae almost as long or longer than pseudorostral spines. Pre-orbital spine roundish to sharp; hiatus between supraorbital eave and post-orbital lobe wide, U-shaped; post-orbital lobe terminally blunt. Basal antennal article longer than broad, outer margin slightly curved to straight margin. Third maxilliped with ischium subquadrate; anterolateral margin of merus weakly produced. Cheliped with margins of merus, carpus, propodus, and palm of chelae carinate. Ambulatory legs slender and cylindrical, merus, carpus and propodus smooth, not carinate, covered with setae, smooth when denuded; P2 longest. Male thoracic sternites 3 and 4 fused without median sutures; lateral margins of sternites 3 and 4 slightly constricted, surface concave. Male pleon triangular, all somites and telson free. Adult female pleon rounded, with all somites and telson free ( Fig. 16A, B View FIGURE 16 ). G1 with single distal angle; G2 shorter than G1, with distal tip rounded ( Fig. 18 View FIGURE 18 A–F).

Etymology. The new genus is named after the characteristic thick layer of setae covering the entire carapace and legs of the crab—“ crocydo ” meaning downy fibers on woollen cloth in Latin, which is originally a Greek word, “ krokydos ”. It is used in arbitrary combination with the Latin word “ carcinus ” from the Greek word “ karkinus ” for crab. Gender masculine.

Remarks. This new genus is morphologically similar to Tunepugettia Ng, Komai & Sato, 2017 , in general carapace form and having relatively wide male thoracic sternites 3 and 4 with slightly constricted lateral margins and a concave surface. Crocydocinus n. gen., however, differs from Tunepugettia in having the carapace regions more clearly defined, often with granules on each region ( Figs. 13 View FIGURE 13 , 14 View FIGURE 14 ) (versus carapace regions defined by strongly swollen regions and usually with no or few granules in Tunepugettia ; Fig. 11A, D View FIGURE 11 ); the pseudorostral spines are short and straight, cylindrical and diverging to form a distinct V-shaped structure ( Figs. 13 View FIGURE 13 , 14 View FIGURE 14 ) (versus pseudorostral spines short, straight, slightly dorso-ventrally flattened with the outer margin slightly curved in Tunepugettia ; Fig. 11A, D View FIGURE 11 ); the postorbital lobe is slender with a rounded distal margin ( Fig. 17 View FIGURE 17 ) (versus cup-like postorbital lobe with the side slightly flatten in Tunepugettia ; Fig. 11C, F View FIGURE 11 ); the basal antennal article has a relatively straight to slightly convex outer margin with distal angle distinct ( Figs. 15 View FIGURE 15 , 16 View FIGURE 16 ) (versus outer margin of basal antennal article prominently convex with distal angle less pronounced in Tunepugettia ; Fig. 11B, E View FIGURE 11 ); the telson of the male pleon is generally more dome shaped ( Figs. 15A, D View FIGURE 15 , 16C View FIGURE 16 ) (versus the telson of the male pleon is more triangular in Tunepugettia ; Fig. 11B, E View FIGURE 11 ); and the ambulatory legs are smooth with the merus, carpus and propodus not carinate ( Figs. 13 View FIGURE 13 , 14 View FIGURE 14 ) (versus ambulatory legs with margins of merus, carpus and propodus directly carinate in Tunepugettia ; Fig. 11A, D View FIGURE 11 ).

The G1s of all the species of Tunepugettia end in a bilobed tip ( Figs. 12 View FIGURE 12 ; Ng et al. 2017: fig. 7); while in almost all species of Crocydocinus n. gen., the G1 distal tip is simple ( Figs. 18 View FIGURE 18 , 19 View FIGURE 19 E–H); the exception being C. decipata ( Williams & Eldredge, 1994) ( Fig. 19 View FIGURE 19 A–D). In the form of the basal antennal article and non-carinate ambulatory legs, however, C. decipata should be transferred to Crocydocinus n. gen.

With the description of four new species from Papua New Guinea, Philippines, and Vanuatu, and the transfer of four species to Crocydocinus n. gen.: C. beauchampi ( Alcock & Anderson, 1894) comb. nov., C. brevirostris ( Doflein, 1904) comb. nov., C. crosnieri (Griffin & Tranter, 1986) comb. nov., and C. decipata ( Williams & Eldredge, 1994) comb. nov., there are eight species in this new genus.