Paramaja Kubo 1936
Creators: name: Ng, Peter K. L.
name: Forges, Bertrand Richer De
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Majidae
Paramaja

description: Paramaja Kubo, 1936   
 Paramaja Kubo, 1936: 361.   
 Paramajella Balss, 1957: 1628 [unnecessary replacement name for Paramaja Kubo, 1936].   
 Maja – T. Sakai, 1938: 296 (part). – T. Sakai, 1965: 83 (part). (not Maja Lamarck, 1801).   
 Diagnosis. Carapace rounded in adults; dorsal surface evenly inflated, covered by granules or tubercles; gastric and branchial regions clearly delimited by grooves (Figs. 8–12). Intestinal region without distinct median spine (Figs. 8–14). Pseudorostral spines relatively short, diverging, forming a V (Figs. 8–13). Supraorbital eave with anterior part longitudinally narrow, rectangular, not prominently expanded; antorbital spine sharp (Fig. 36G–K). 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 (Fig. 36G–K). Lateral carapace margin with 3 or 4 spines and numerous tubercles, branchial region with larger tubercle, not discernible from other surrounding tubercles in large specimens (Figs. 8–13). Posterior carapace margin with 2 short median spines, not visible from dorsal view when adult due to swollen carapace (Figs. 8–12). Eyes relatively short, slender, with large ovoid cornea (Fig. 36G–K). Antennal flagellum short, slender. Basal antennal article longer than broad, rectangular; surface with several tubercles, with 2 blunt 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 but does not significantly overlap distal part of basal antennal article (Fig. 39G–K). Epistome much wider than long, anterior margin unarmed; posterior margin composed of 4 rectangular plates separated by shallow fissures (Figs. 39G–K, 41E, F). Suborbital margin separated from basal antennal article by short fissure, confluent with margin of postorbital tooth (Fig. 39G–K). Outer surface of third maxilliped covered by short setae in adults; ischium subrectangular, distinctly longer than broad; postero-external angle of merus relatively broad, “inserted” into shallower concavity on outer margin of ischium; antero-internal part of ischium rounded, auriculiform (Fig. 43I–P). Male chelipeds relatively short in adult males, surfaces of merus and carpus almost smooth or with very small granules; 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. 8–12, 53I–L). 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. 6H, 8– 12, 55E–J). Thoracic sternum wide; surfaces of somites 5–8 with numerous prominent rounded tubercles and granules; sternites 3 and 4 slightly depressed; margin between sternites 2 and 3 demarcated by deep notch; anterior margin of sterno-abdominal cavity not forming complete rim (Figs. 48, 52D). Male abdomen subrectangular, with 6 free somites and telson; somites 3–6 and telson subequal in width (Fig. 48). Male press-button abdominal locking mechanism submedian in position on sterno-abdominal cavity (Fig. 52D). Female abdomen dome-shaped, covering most of thoracic sternum. G1 very long, slender, almost straight for most of length, distal part gently curved, subconical with rounded tip, with small, low subdistal dorsal flap, with scattered setae (Fig. 15).   
 Type species. Paramaja kominatoensis Kubo, 1936, by original designation and monotypy. Gender feminine.   
 Remarks. Kubo (1936: 361) established a new genus for a new species from Kominato, Japan, with the following comments: “The present genus stands somewhat intermediate between the two genera Maja and Majopsis (sic for Maiopsis Faxon, 1893), and it is easily distinguished from the genus Maja in lacking any spines on carapace, and from the genus Majopsis in having no accessory spine on rostral spines, but two spines on distal margin of basal segment of outer antennae, and fingers of chela not canaliculate within.” Although none of these characters work at present to distinguish Paramaja from Maja s. str. or allied genera, it can still be separated by other features.   
 Paramaja Kubo, 1936, is here resurrected to accommodate Indo-Pacific species which have a uniformly inflated carapace which has the dorsal surface covered with granules and tubercles: P. gibba (Alcock, 1895), P. kominatoensis Kubo, 1936, and P. turgida n. sp. The genus is also characterised by features of its suborbital margin, epistome, male abdomen and G1 structure.   
 Paramaja is closest to Alcomaja n. gen., with which it shares a suite of carapace, antennal, epistomal, third maxilliped, pereiopodal, thoracic sternal and male abdominal characters. The single most important character separating Paramaja from Alcomaja is the form of the G1. In Paramaja, the G1 is very long and mostly straight, the distal part being conical (Fig. 15). In Alcomaja, the G1 is proportionately shorter, more curved, and part of the dorsal fold bends downwards to form a distinct ventral projection (Figs. 19, 20). Species of Alcomaja also have relatively longer and more slender pseudorostral spines (Fig. 36L–O) than in Paramaja (Fig. 36G–K). Adults of the two genera are easy to separate, with Paramaja growing to much larger sizes (over 60–70 mm carapace length) while Alcomaja species are smaller. In Paramaja specimens, even when small (20–30 mm carapace length), the branchial and cardiac regions are proportionately more inflated and the lateral and branchial spines are relatively shorter (Figs. 10A, B, 11A–C, 12A, B). Specimens of Alcomaja of comparable size on the other hand have less inflated branchial and cardiac regions, and the lateral and branchial spines are stronger and longer (Figs. 16, 17). That said, juvenile female specimens of the two species can be difficult to separate.
description: Published as part of 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, pp. 110-225 in Raffles Bulletin of Zoology 63 on pages 131-132, DOI: 10.5281/zenodo.5384590