Danarma eurymerus
Creators: name: Schubart, Christoph D.
name: Ng, Peter K. L.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Sesarmidae
Danarma
Danarma eurymerus

description: Danarma eurymerus (Davie & Ng, 2013)
(Figs. 13C, 14C, D, 19D, E, J–N, 43F)
Chiromantes obtusifrons – Liu, 2009: 41, fig. 10. [not Sesarma obtusifrons Dana, 1851]
Chiromantes eurymerus Davie & Ng, 2013: 21, figs. 3I, J, 4D, 5E, 6E, 7E, 9E, 14; Li & Chiu, 2013: 39; Ng et al., 2017b: 103.
Material examined. Holotype male (18.7 × 14.8 mm) (NMNS 7028-002), west coast of Lanyu Island, Taiwan, calcareous rock terraces, spray zone, coll. C.D. Schubart & H.-C. Liu, 20–21 September 1999 [DNA voucher taken but needs to be checked against C. leptomerus] (ex ZRC 2000.1860). Paratypes: 1 male (20.0 × 15.4 mm) (QM- W29171), same data as holotype; 1 male (18.2 × 14.0 mm), 2 females (17.0 × 13.2 mm, 19.9 × 15.0 mm) (ZRC 2000.1823), Pingtung County, Hsiang Chiaowan, Taiwan, coll. H.-C. Liu, 25 August 1999; 1 male (13.3 × 10.2 mm) (ZRC 2000.1822), Pingtung County, Hsiang Chiaowan, Taiwan, coll. H.-C. Liu, 5 July 1999; 1 male (19.3 × 14.8 mm), 1 female (22.6 × 16.7 mm) (NMMBA 3504 b), coll. Hsiang-Chiau-Wan, Kenting, Pingtung County, Taiwan, coll. C.C. Li, 23 August 2012; 2 males (17.5 × 13.4 mm, 16.7 × 12.3 mm) (NMNS), Siatanzai, Kenting, Pingtung County, 21°55′36.6″N 120°44′21.8″S, Taiwan, coll. J.-H. Lee & W.-J. Wang, 17 August 2012; 1 male (15.4 × 12.3 mm), 1 ovigerous female (18.0 × 13.4 mm) (ZRC 2012.0956), 1 female (18.8 × 13.6 mm) (NMNS), Siatanzai, Kenting, Pingtung County, 21°55′36.6″N 120°44′21.8″S, Taiwan, coll. J.-H. Lee & W.-J. Wang, 31 August 2012. Others: TAIWAN – 1 dried female exuvium (24.8 × 18.7 mm) (ZRC 2012.0957), Dingtanzai, near nuclear power station, Kenting, Pingtung County, coll. P.K.L. Ng, 4 October 2012.
Diagnosis. Carapace transversely subovate, ca. 1.3 times broader than long; dorsal carapace, lateral branchial regions markedly swollen; external orbital tooth with outer margin broadly convex marking widest point of carapace; front ca. 0.65–0.7 times carapace width, margin broadly convex in frontal view, but medial part relatively straight in dorsal view, appears smooth but microscopically granular, with pair of low lateral swellings behind margin; supraorbital margin entire, semicircular; dorsal surface of carpus of cheliped covered in small granules; ambulatory legs relatively short; merus of third ambulatory leg ca. 2.0 times longer than wide; that of fourth ambulatory leg similar at 2.0–2.1 times longer; fourth ambulatory propodus 2.1–2.2 times; male pleon moderately broad; somite 6 with distolateral margins relatively straight, strongly divergent, margins convex overall; somite 3 width 3.1 times basal width of telson; G1 markedly stout, with margins subparallel to obtusely angled subdistal shoulder; distally slender, strongly bent to 45° angle; distal chitinous process short, not projecting past line of gonopod shaft, moderately tapering. (After Davie & Ng, 2013: 21).
Colour. “Carapaces of adult males and females are generally pale grey and white to yellowish-brown to yellowish-grey; with chelae of both sexes, notably dactylus, white, without obvious pink or red; eyes blue to bluish-green.” (Davie & Ng, 2013: 22, fig. 3I, J).
Remarks. The taxonomy of this species has been treated by Davie & Ng (2013). As observed by Davie & Ng (2013: 7, 22), D. eurymerus is markedly different from all congeners in having a G1 that is proportionately much stouter, with the distal chitinous part short and subtruncate (Fig. 15J–M). In all other Danarma species, the G1 is slender and the distal chitinous part is long (Fig. 15F–I). It is most unusual for congeners to have such a dissimilar G1, and it may be a consequence of natural selection by character displacement to reduce or prevent hybridisation (see General discussion). In any case, the genetic data supports the monophyly of all the Danarma species.
The record of “ Stelgistra stormi ” by Lee (2008: 137) from Taiwan is mixed. One photograph is S. stormi (De Man, 1895) while the other with blue eyes is clearly a specimen of D. eurymerus.
Biology. This species lives in crevices or under rocks in the supralittoral karst zone. It has been found together with D. leptomerus (Davie & Ng, 2013: 24).
Distribution. Known only from Taiwan and Ryukyus, Japan (Davie & Ng, 2013).
description: Published as part of Schubart, Christoph D. & Ng, Peter K. L., 2020, Revision of the intertidal and semiterrestrial crab genera Chiromantes Gistel, 1848, and Pseudosesarma Serène & Soh, 1970 (Crustacea: Brachyura: Sesarmidae), using morphology and molecular phylogenetics, with the establishment of nine new genera and two new species, pp. 891-994 in Raffles Bulletin of Zoology 68 on page 926, DOI: 10.26107/RBZ-2020-0097, http://zenodo.org/record/5351295