Cancer scarpellonis Curtiss, 1938

Ng, Peter K. L., Eldredge, Lucius G. & Evenhuis, Neal L., 2011, The names of decapod and stomatopod Crustacea from Tahiti, French Polynesia, established by Anthony Curtiss in 1938 and 1944, Zootaxa 3099, pp. 43-56 : 50

Cancer scarpellonis Curtiss, 1938 [toetoe]

Grapsus crinipes Dana, 1851: 249 .

Cancer scarpellonis Curtiss, 1938: 173 , n. syn.

Curtiss (1938: 172) identified a group of crabs Tahitians call “ toetoe ” that live “in cliffs overhanging the sea, where the waves beat”. The descriptions of the morphology and habits of Cancer scarpellonis and C. ballantei (see below) leave no doubt that both are grapsids of the genera Grapsus or Geograpsus . As both C. scarpellonis and C. ballantei were described as having “behind each eye, on the side of the upper shell … a single spine, and a tooth behind it” ( Curtiss 1938: 173), they also cannot be species of Pachygrapsus or even Metopograpsus (Grapsidae) , members of which have entire lateral carapace margins. They are unlikely to be species of Plagusia (Plagusiidae) or Percnon (Percnidae) as members of both these genera do not live in the supralittoral zone, having fully aquatic habits even if they may live in the surf zone of the intertidal. Plagusia species have in addition two teeth behind the external orbital tooth.

Cancer scarpellonis was described as being “an inch wide, and almost square in form … The joints of the pincer-legs nearest the body have a toothed crest on the upper side. The four hinder pairs have white bristles on them, a quarter of an inch long … body is olive brown above, whitish underneath” ( Curtiss 1938: 173). This description perfectly matches species of Geograpsus , which have the inner margin of the merus of the cheliped prominently dilated and armed with numerous sharp teeth; and the propodi and dactyli of the ambulatory legs are lined with long stiff almost vertical setae. While generally acknowledged as semiterrestrial and can be found some distance inland, two species, Geograpsus crinipes ( Dana, 1851) and Geograpsus stormi De Man, 1895 , are often found in or near sea cliffs. The colours of the carapace and leg setae best match Geograpsus crinipes . The colour of its carapace and legs varies from whitish cream to dark grey, but is most often olive-brown; and the vertical bristles on the ambulatory legs are yellowish white. The other Geograpsus species on Tahiti, G. grayi (H. Milne Edwards, 1853) ( Poupin & Juncker 2010) has more terrestrial habits, living on the forest floor beyond the supralittoral zone, and has a purple carapace with dark bristles. Geograpsus stormi has a red carapace with orange to yellow ambulatory leg bristles.