Alcomaja, Ng & Forges, 2015

Ng, Peter K. L. & Forges, Bertrand Richer De, 2015, Revision of the spider crab genus Maja Lamarck, 1801 (Crustacea: Brachyura: Majoidea: Majidae), with descriptions of seven new genera and 17 new species from the Atlantic and Indo-West Pacific, Raffles Bulletin of Zoology 63, pp. 110-225 : 144-145

publication ID	https://doi.org/ 10.5281/zenodo.5384590
publication LSID	lsid:zoobank.org:pub:40BCDD62-D35E-46D1-95A3-2CC0DF219DEE
persistent identifier	https://treatment.plazi.org/id/C3EE8C3E-4F10-433C-B1FA-974B8F3E563E
taxon LSID	lsid:zoobank.org:act:C3EE8C3E-4F10-433C-B1FA-974B8F3E563E
treatment provided by	Valdenar
scientific name	Alcomaja
status	gen. nov.

Treatment

Alcomaja View in CoL n. gen.

Diagnosis. Carapace ovate; dorsal surface convex, covered by granules or tubercles; gastric and branchial regions delimited by distinct grooves ( Figs. 16 View Fig , 17 View Fig ). Intestinal region without distinct median spine ( Figs. 16 View Fig , 17 View Fig ). Pseudorostral spines long, diverging, forming a V, ( Figs. 18 View Fig , 36L–O View Fig ). Supraorbital eave with anterior part longitudinally narrow, rectangular, not prominently expanded; antorbital spine sharp ( Figs. 18 View Fig , 36L–O View Fig ). Intercalated spine distinct, separated from supraorbital eave and postorbital spine by distinct gaps; postorbital spine strong, lobiform; hepatic region with 1 strong spine, much shorter than postorbital spine; 1 or more smaller spines below ( Figs. 18 View Fig , 36L–O View Fig ). Lateral carapace margin with 3 spines and numerous tubercles or granules, 1 branchial spine or tubercle usually discernible, may be low in large specimens ( Figs. 16 View Fig , 17 View Fig ). Posterior carapace margin with 2 short median spines ( Figs. 16 View Fig , 17 View Fig ). Eyes relatively long, slender, with ovoid cornea ( Figs. 18 View Fig , 36L–O View Fig ). Antennal flagellum short, slender. Basal antennal article longer than broad, rectangular; surface with several tubercles or granules, with 2 spines distally; inner and outer lateral margins may have low granules or lobes, or entire; proximal outer angle rounded; antero-external crested rim of antennular fossa touches does not substantially overlap basal antennal article ( Fig. 39L–O View Fig ). Epistome as wide as long, anterior margin with low lobes or low swellings; posterior margin composed of 4 rectangular plates separated by shallow fissures ( Figs. 39L–O View Fig , 41G, H View Fig ). Suborbital margin separated from basal antennal article by short fissure, confluent with margin of postorbital tooth ( Fig. 39L–O View Fig ). Outer surface of third maxilliped covered by very short setae in adults; ischium subrectangular, distinctly longer than broad; posteroexternal angle of merus relatively broad, “inserted” into shallower concavity on outer margin of ischium; anterointernal part of ischium rounded, auriculiform ( Fig. 45A–H View Fig ). Male chelipeds relatively short in adult males, surfaces of merus and carpus almost smooth to covered with very small granules, low longitudinal ridges with low tubercles; carpus short, with low, uneven longitudinal ridge; propodus of palm elongated, curved, smooth, without lateral cristae in young, short, inflated in adults, palm longer than fingers; fingers long, slender, gently curved, with distinct basal gape when closed ( Figs. 16 View Fig , 17 View Fig , 53M–P View Fig ). Ambulatory legs relatively long, slender; merus without dorsal subdistal spine; dactylus elongate, curved, covered with long setae when young except for corneous tip, almost completely smooth in adults ( Figs. 16 View Fig , 17 View Fig , 55K–N View Fig ). Thoracic sternum wide; surfaces of somites 5–8 with numerous prominent rounded tubercles and granules; sternites 3 and 4 distinctly depressed; margin between sternites 2 and 3 demarcated by deep notch; anterior margin of sterno-abdominal cavity not forming complete rim ( Figs. 49 View Fig , 52E–G View Fig ). Male abdomen subrectangular, with 6 free somites and telson; somites 3 and 4 subequal to or slightly wider than somites 5, 6 and telson ( Fig. 49 View Fig ). Male press-button abdominal locking mechanism submedian in position on sterno-abdominal cavity ( Fig. 52E–G View Fig ). Female abdomen dome-shaped, covering most of thoracic sternum. G1 long, slender, gently curved, distal part subconical with rounded tip, dorsal part folding downwards to form ventral projection, with scattered setae on ventral surface and numerous short setae on dorsal surface ( Figs. 19 View Fig , 20 View Fig ).

Type species. Alcomaja irrorata View in CoL n. sp. by present designation.

Etymology. The genus is named after Alfred William Alcock. The name is an arbitrary combination of his family name with Maja . Gender feminine.

Remarks. Alcomaja n. gen. is established to accomodate A. irrorata n. sp., Maja gracilipes Chen & Ng, 1999 , M. confragosa Griffin & Tranter, 1986 , M. nagashimaensis T. Sakai, 1969 , A. desmondi n. sp., A. miriky n. sp., and A. latens n. sp.

In the form of the suborbital margin, basal antennal article, epistome, third maxilliped, pereiopods, thoracic sternum and male abdomen, Alcomaja is most similar to Paramaja Kubo, 1936 . The differences have been discussed under the remarks for that genus.