Rathbunaja ursus, 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 : 216

publication ID	https://doi.org/ 10.5281/zenodo.5384590
publication LSID	lsid:zoobank.org:pub:40BCDD62-D35E-46D1-95A3-2CC0DF219DEE
DOI	https://doi.org/10.5281/zenodo.5466833
persistent identifier	https://treatment.plazi.org/id/EA0364F5-146A-4288-929C-60D73C5D0A3B
taxon LSID	lsid:zoobank.org:act:EA0364F5-146A-4288-929C-60D73C5D0A3B
treatment provided by	Valdenar
scientific name	Rathbunaja ursus
status	sp. nov.

Treatment

Rathbunaja ursus View in CoL n. sp.

( Figs. 60 View Fig , 61G, H View Fig , 63E–H View Fig , 64E, F View Fig , 65H–K View Fig , 67A–D View Fig )

Material examined. Holotype: male (50.1 × 41.5 mm) ( NMCR, ex ZRC 2013.1275 View Materials ), Balicasag Island, Panglao, Bohol, Philippines , 200–300 m, coll. fishermen with tangle nets, 2 March 2004 . Paratypes: Philippines – 2 ovigerous females (46.8 × 36.6 mm, 45.0 × 36.0 mm) ( ZRC 2001.0594 View Materials ), Balicasag Island, Panglao , Bohol, 200–300 m, coll. fishermen with tangle nets, 28 November 2001 . — 1 male (41.6 × 32.8 mm), 1 ovigerous female (45.6 × 35.7 mm), 1 female (47.2 × 37.6 mm) ( ZRC 2013.1276 View Materials ), Balicasag Island, Panglao , Bohol, 200–300 m, coll. fishermen with tangle nets, June 2002 . — 1 female (49.4 × 38.4 mm) (NSMT-Cr 15386), Balicasag Island, Panglao , Bohol, coll. fishermen with tangle nets, via H. Komatsu & M. Takeda, February 2003 . — 1 male (47.5 × 39.5 mm) ( ZRC 2013.1277 View Materials ), Maribohoc Bay, Panglao , Bohol, coll. J. Arbasto, tangle nets, 30 May 2004 .

Diagnosis. Carapace relatively broad ( Fig. 60 View Fig ). Pseudorostral spines long, diverging ( Fig. 60 View Fig ). Median row with 2 median gastric spines; 2 cardiac spines; 2 intestinal spines ( Fig. 60 View Fig ). Basal antennal article with 2 relatively long distal spines, strongly diverging ( Fig. 61G View Fig ). Ischium of third maxilliped long ( Fig. 63E–H View Fig ). Ambulatory legs (notably merus and propodus) relatively long ( Figs. 60 View Fig , 65I–K View Fig ). Male telson appears semicircular ( Fig. 64E View Fig ). G1 very long, strongly curved, slender, tip bent inwards ( Fig. 67A–D View Fig ).

Etymology. The name “ursus” alludes to the thick tomentum covering the animal like the fur of a bear, «ursus». The name is used as a noun in apposition.

Remarks. The discovery of Rathbunaja ursus n. sp. from Balicasag, Philippines, is rather surprising especially since there was also a specimen of R. bisarmata ( Rathbun, 1916) collected from the same area. Most specimens of Rathbunaja from the Philippines actually belong to this new species. The two species are similar and are not easy to separate; In R. ursus , however, the carapace is relatively broader ( Fig. 60 View Fig versus Fig. 59A, B View Fig ), the two distal spines on the basal antennal article are more strongly diverging ( Fig. 61G View Fig versus Fig. 61A, C View Fig ), the ischium of the third maxilliped is proportionately longer ( Fig. 63E–H View Fig versus Fig. 63A, B View Fig ), the anterior thoracic sternum (sternites 1–4) is relatively longer ( Fig. 64E, F View Fig versus Fig. 64A, B View Fig ), the male telson is proportionately broader ( Fig. 64E, F View Fig versus Fig. 64A, B View Fig ), and the lateral margins of male abdominal somites 5 and 6 are more concave ( Fig. 64E, F View Fig versus Fig. 64A, B View Fig ). Most significantly, their G1 structures are completely different, with that of R. ursus much longer, with the distal part more strongly curved and slender ( Fig. 67A–D View Fig versus Fig. 66A–G View Fig ). These differences cannot be explained by size or maturity.