Glyptoxanthus hancocki Garth, 1939

Mendoza, Jose Christopher E. & Guinot, Danièle, 2011, Revision of the genus Glyptoxanthus A. Milne-Edwards, 1879, and establishment of Glyptoxanthinae nov. subfam. (Crustacea: Decapoda: Brachyura: Xanthidae), Zootaxa 3015, pp. 29-51 : 40-41

Glyptoxanthus hancocki Garth, 1939

( Fig. 6 )

Glyptoxanthus labyrinthicus, Rathbun 1930: 266 (in part). Not Actaea labyrinthicus Stimpson, 1860 .

Glyptoxanthus hancocki Garth, 1939: 15 , pl. 4 fig. 1, pl. 5 figs. 1a, 2a, 3a (type locality: Galapagos Is.); 1946: 437, pl. 76 figs. 1, 2. — Guinot 1967: 556; 1971: 1073; 1979: 68, pl. 6 fig. 8. —Ng et al. 2008: 199 (list).

Material examined. Ecuador (Galapagos Is.): Holotype, female, 25.8 × 18.0 mm ( LACM CR 1938.058.1), stn 796-38, shore rock, Sullivan Bay, James Is., coll. Ve le ro /A. Hancock Pacific Expedition, 21 Jan. 1938. Paratypes: 1 male, 26.8 × 18.5 mm ( LACM CR 1938.058.2), same as holotype; 2 males, 16.0 × 11.0 mm, 32.4 × 21.8 mm ( LACM CR 1933.107.2), stn 101-33, shore, Darwin Bay, Tower Is., coll. Velero /A. Hancock Pacific Expedition, 26 Feb. 1933.

Other material. 1 male, 37.9 × 25.5 mm ( LACM CR 1934.187.2), stn 313-35, shore, Black Beach, Charles Is., coll. Velero /A. Hancock Pacific Expedition, 6 Dec. 1934; 1 male, 19.0 × 13.1 mm, 2 females, 15.9 × 11.0 mm, 19.4 × 13.3 mm ( LACM CR 1938.058.22), stn 796-38, shore, Sullivan Bay, James Is., coll. Velero /A. Hancock Pacific Expedition, 21 Jan. 1938; 1 female, 29.3 × 19.3 mm ( LACM CR 1938.062.2), stn 800-38, shore, Cartago Bay, Albemarle Is., coll. Velero /A. Hancock Pacific Expedition, 22 Jan. 1938; 1 male, 16.2 × 11.3 mm, 2 females, 20.5 × 14.3 mm, stn 803-38, shore, Black Beach, Charles Is., coll. Velero /A. Hancock Expedition, 23 Jan. 1938.

Diagnosis. Carapace transversely ovate, width-to-length ratio about 1.4–1.5; dorsal surface rather depressed; regions well defined, with intervening furrows relatively wide, not less pronounced than cervical groove, setose; vermiculations symmetrically convoluted on left and right side of carapace, smooth, with fewer included cavities compared to congeners; 1F, 2F distinct; 2M completely divided longitudinally, 1M fused to inner branch; 3M completely independent of 2M, but bridged by 4M to 1P; 2L, 3L, 4L distinct, 5L and 6L fused. Anterolateral margin arcuate, divided into 4 weakly projecting lobes. Male thoracic sternum eroded, but with symmetric pattern of ridges and cavities. External surfaces of pereopods similarly sculpted as dorsal carapace. Male abdomen with transverse ridges. G1 not figured.

Remarks. Rathbun (1930) assigned one female specimen from the Galapagos Islands to Glyptoxanthus labyrinthicus (Stimpson, 1960) . Garth (1939, 1946) subsequently assigned this specimen to a new species, Glyptoxanthus hancocki , along with more type material collected from the Galapagos. G. hancocki is most similar to G. labyrinthicus , a Pacific species, based on the general shape and sculpturing of the carapace and thoracic sternum. However, the two can be easily distinguished by the following features: 1) 1F and 2F are not connected to each other in G. hancocki (fused in G. labyrinthicus ); 2) the inner branch of 2M is not fused to the posterior part of 3M (fused in G. labyrinthicus ); 3) the lobes of the carapace anterolateral margin are not well produced (well produced, particularly the fourth lobe, in G. labyrinthicus ); and 4) the carapace vermiculations have fewer punctae, i.e. none on inner branch of 2M and 3 on 3M (vermiculations with more punctae, i.e., about 5 on inner branch of 2M and on 3M, in G. labyrinthicus ).

Garth (1946: 438) described the live colouration of this species as such: “Dark areas on carapace a rich violet carmine, a little more reddish on branchial and posterior areas. Light areas cadmium orange on frontal, gastric, and cardiac regions; branchial and intestinal regions same color but lighter in tone. Chela violet carmine on dark areas; fingers very dark seal brown, fading toward tips, which are almost white. Ambulatory legs burnt lake on dark areas and light cadmium orange on light areas. Nail of dactyl amber. Eyestalk pale orange yellow; eye blackish brown.”

Ecology and geographical distribution. Glyptoxanthus hancocki is known only from the Galapagos Islands, off the coast of Ecuador. It has been collected from rocky substrate (usually under large rocks) in the intertidal zone, during very low tides (see Garth 1946).

Figures

FIGURE 6. Glyptoxanthus hancocki Garth, 1939, paratype, male, 32.4 × 21.8 mm (LACM CR 1933.107.2), Galapagos Is.: A, dorsal view; B, anterior view; C, ventral view; D, right chela, external view.