Glyptoxanthus A. Milne-Edwards, 1879

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 : 33

Glyptoxanthus A. Milne-Edwards, 1879

Glyptoxanthus A. Milne-Edwards, 1879: 253 . — Bouvier 1922: 62. — Rathbun 1930: 263. — Garth 1939: 15; 1946: 437. — Guinot 1967: 554; 1971: 1072; 1979: 65. — Manning & Holthuis 1981: 135. — Serène 1984: 81. — Williams 1984: 398. —Ng et al. 2008: 199 (list). — De Grave et al. 2009: 43 (list).

Actäa (in part), Klunzinger 1913: 185 [89].

Actaea (in part), Odhner 1925: 35, 57.

Actaea (Glyptoxanthus), Monod 1956: 219 . — Serène 1961: 198.

Type species. Actaea erosa Stimpson, 1859 , subsequent designation by Rathbun 1930; gender masculine.

Diagnosis. Carapace transversely ovate, broader than long, width-to-length ratio about 1.4, thick when viewed head-on or from the side; regions more-or-less defined but often entirely or partially coalesced, dorsal surface typically ornamented with prominent ridges formed by fused granules, arranged in regular reticulate or vermiculate patterns, surrounded by dense setae; cervical groove between gastro-cardiac and branchial regions deep. Front deflexed, quadrilobate, with deep median notch and deep, lateral concavities on anterior margin. Anterolateral margins long, arcuate, divided into 4 low lobes, anterior part descending toward buccal cavity; posterolateral margins shorter, deeply concave; posterior margin straight. Suborbital regions eroded; subhepatic and pterygostomian regions granulate, setose, subhepatic region with narrow canals continuing from furrows on dorsal surface.

Orbits small, round. Antennules folding obliquely. Anterior part of proepistome touching and almost protruding through deep, median notch of front. Basal article of antenna large, subtrapezoidal, advanced ventrally, and not sunken between front and infraorbital tooth; flagellum short, entering orbital hiatus. Epistome small, posterior margin with 2 prominent notches laterally. Posterior part of endostome with prominent oblique ridges. Lacinia of mxp1 not produced transversely. Mxp3 eroded; anterior margin of merus deeply notched; ischium with deep, submedian sulcus; mesial margin of exopod bulging into matching concavity on ischium, distal end deflected laterally.

Thoracic sternum narrow, deeply eroded, often with reticulate sculpturing; sternite 1 and 2 completely fused, separated from sternite 3 by deep suture; sternite 3 and 4 partially fused at center; median cavity on sternite 4 just anterior to male telson, with short median line within; sterno-abdominal cavity deep; press-button prominent, placed on posterior half of sternite 5; sternite 7 narrow, with anterior portion slightly larger than episternite, which in turn locks very firmly with lateral expansions of abdominal somite 3; sternite 8 entirely covered by abdomen.

Pereopods very tightly coapted to the carapace and to one another. Chelipeds equal, robust, fingers stout and blunt; external surfaces of carpus and palm with granulate, vermiculate lobules surrounded by short setae and deep furrows; merus short, granulate; dactylus and fixed finger with deep, longitudinal channels on external surface, with large, granulate tuberosity on supero-proximal end of dactylus. Ambulatory legs short, flattened; sculpturing on external surfaces similar to that in chelipeds.

Male abdomen long, constricted at junction of somites 5 and 6, tip of telson just reaching level of coxo-sternal condyles of cheliped coxae; outer surface with pronounced transverse ridges and vermiculations; somites 3–5 immovably fused, but with sutures visible and complete on external surface; somite 3 with abrupt lateral expansions, equipped with cupuliform depressions which receive and interlock with episternite of sternite 7.

G1 long, slender, bluntly tipped, opening apically; distal half armed with spiniform tubercles, sometimes with short, simple setae, never with long, plumose, subterminal setae. G2 about one-fourth length of G1.

Remarks. Glyptoxanthus species are rare to uncommon, and are usually found from the intertidal zone to moderate depths (0–90 m), usually in rocky substrate, and distributed along the western and eastern coasts of the Americas, the Caribbean Sea, the western coast of Africa, and the Red Sea. The different taxa are easily separable by the pattern of the vermiculations on the dorsal surface of the carapace. Their live coloration (variegated or mottled) and their morphology suggest that they are probably sedentary, relying on camouflage to avoid potential predators. Not much is known about their ecology, save for some remarks on the nature of the substrates and the depths from which they have been sampled (e.g., Garth 1946; Manning & Holthuis 1981).