Conchoecetes Stimpson, 1858

Naruse, Tohru, 2019, Revision of the shell-carrying crab genus Conchoecetes Stimpson, 1858 (Crustacea: Brachyura: Dromiidae), Zootaxa 4706 (1), pp. 1-47 : 3

Conchoecetes Stimpson, 1858

Conchoecetes Stimpson 1858: 226 ; 1907: 180; Haswell 1882: 141; Henderson 1893: 407; Alcock 1899: 41; 1901: 40; Borradaile 1903: 301; Stebbing 1910: 346; 1920: 253; Ihle 1913: 59; Barnard 1950: 308; Serène & Lohavanijaya 1974: 12; Sakai 1976: 26; Dai & Yang 1991: 30; Lewinsohn 1984: 119; McLay 1993: 174; Guinot & Tavares 2000: 301; Davie 2002: 159; Ahyong et al 2009: 30; Guinot & Wicksten 2015: 591.

Conchoeodromia Chopra, 1934: 477 (type species Conchoeodromia alcocki Chopra, 1934 ).

Type species. Dromia artificiosa Fabricius, 1798 , gender masculine.

Diagnosis. Carapace as wide as or slightly wider than long; mostly flattened, subpentagonal, sometimes posterior cardiac and branchial areas poorly calcified; cervical and branchial grooves usually distinct; surface granular to almost smooth, with fine tomentum; front narrow, tridentate, lateral teeth well developed, median rostral tooth lower than lateral teeth; anterolateral margin variable, may be unarmed not marked by a distinct edge or with an edge that may bear small teeth and interrupted by one or more notches; cervical and branchial grooves usually marked by distinct teeth on margin. Chelipeds granular; with epipod. P2 and P3 dactyli fringed with setae and many minute adpressed spines on ventral margin; propodi without distal spine. P4 larger than P5; dactylus enlarged, talon-like, occluding with stout proximal propodal extension; used for carrying bivalve shell. P5 small; segments flattened, dactylus small simple, upturned; propodus without distal spine occluding with dactylus. Pleon of 6 free somites and telson. Uropod plates well-developed, visible externally; forming pleon holding mechanism by locking against strong prominence on P2 coxae. Male gonopods consisting of three articles: G1 stout, semi-rolled, setose tube; G2 as long as G1 needle-like. Female 7/8 sternal sutures normally end apart on erect tube-like structures between or near chelipeds (modified after McLay 1993).

Remarks. The species of Conchoecetes are most easily distinguished by carapace shape and characters associated with variation in the anterolateral margin. The degree of curvature of the carapace surface has an effect on the definition of the cervical and branchial grooves and shape of the anterolateral margin. We can contrast C. intermedius which has a gently curved carapace surface, on which the cervical and branchial grooves are scarcely marked, which merges gradually into the hepatic area without a distinct margin or teeth, with C. artificiosus which has a flat carapace surface deeply marked by the grooves and pronounced structured anterolateral margin with teeth and notches. Here we find the type specimen invaluable as a reference point with which all the former “ C. artificiosus ” material can be compared to demonstrate differences which warrant recognition of several new species. The result is that type species Conchoecetes artificiosus appears to be restricted to the Western Indian Ocean in the vicinity of the Indian sub-continent. We re-describe and provide photographs of the type specimens for each species.