Danarma obtusifrons ( Dana, 1851 )

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, Raffles Bulletin of Zoology 68, pp. 891-994 : 922

Danarma obtusifrons ( Dana, 1851)

( Figs. 13A , 14A , 18A , 19A–C, F–I , 43E )

Sesarma obtusifrons Dana, 1851: 250 ; Dana, 1852: 355, pl. 22, fig. 9; H. Milne Edwards, 1853: 183; De Man, 1887: 644; Lenz, 1901: 472; Titcomb et al., 1979: 367; Godwin & Bolick, 2006: 39, 49.

Sesarma (Holometopus) obtusifrons – Rathbun, 1906: 840; 1907: 35; Tesch, 1917: 179 (part); Edmondson, 1946: 306, fig. 183e; Edmondson, 1959: 185, figs. 13c, 17c; Serène, 1968: 107 (part).

Chiromantes obtusifrons – Ng & Liu, 1999: 230.

“ Chiromantes ” obtusifrons – Ng et al., 2008a: 220, 224 (part); Castro, 2011: 120 ; Davie & Ng, 2013: 2, figs. 1, 4A, 5A, B, 6A, B, 7A, B, 8A, 9A, B, 10A, 11.

Incertae sedis [see remarks later] (see Davie & Ng, 2013: 7)

Sesarma (Sesarma) obtusifrons – De Man, 1895: 161; De Man, 1898: pl. 29, fig. 31.

Material examined. 2 males (16.8 × 12.9 mm, 19.7 × 14.7 mm) ( ZRC 2002.0220 , ex. BPBM-266), Malaikahana, Oahu, Hawaii, C.M. Cooke et al., 8 July 1916 ; 1 male (17.7 × 13.2 mm), 1 female (15.7 × 11.6 mm) ( UF-FLMNH 14837 ), 21.2833°N 157.667°E, Coco Head, Oahu, Hawaii, coll. G. Paulay et al., October 2006 .

Diagnosis. Carapace transversely rectangular, ca. 1.3 times broader than long; dorsal carapace, lateral branchial regions weakly convex, not prominently swollen; external orbital tooth with outer margin broadly convex so greatest carapace width clearly posterior to external orbital tooth; front ca. 0.65 times carapace width, margin broadly convex in frontal view with medial part relatively straight in dorsal view, beaded with row of small but distinct granules, with pair of low lateral swellings behind margin; supraorbital margin entire, semicircular; dorsal surface of cheliped carpus covered in small but conspicuous granules; ambulatory legs relatively short; third ambulatory merus ca. 2.2 times longer than wide; fifth ambulatory merus ca. 2.3 times longer; fourth ambulatory propodus ca. 2.2 times longer; male pleon moderately broad; somite 6 with distolateral margins strongly divergent, relatively straight over distal two-thirds; somite 3 width 2.9 times basal width of telson; G1 relatively slender, weakly tapering to obtusely angled subdistal shoulder; distally slender, strongly bent to 45° angle; distal chitinous process long, with slender narrow apex, dorsal margin slightly concave. (After Davie & Ng, 2013: 2).

Colour. “Background colour of carapace, legs fawn to bluish gray, covered in fine darker speckling with scattering of slightly larger irregular spots. Legs with darker, broad transverse bands that are more noticeable on the carpi and meri. Chelipeds dorsally similar in colour to carapace and legs but becoming greyish white in frontal and ventral view. Ocular peduncles and corneas pale, similar to carapace in colour.” ( Davie & Ng, 2013: 5; fig. 1).

Remarks. This characteristic species has been reported from a wide area from the eastern Indian Ocean to Hawaii (type locality). Davie & Ng (2013) revised the taxonomy of the species and recognised four new species. All these species share the diagnostic generic features of the genus. Although the type(s) of Sesarma obtusifrons Dana, 1851 , are almost certainly lost, Davie & Ng (2013) argued that there was no need to designate a neotype as the species is distinctive and easily distinguished for all known congeners.

Biology. “ Edmondson (1959) noted that C. obtusifrons was found intertidally and “even above the high water mark”, and Paulay & Starmer (2011: 11) reported finding it living in a supratidal boulder field on O‘ahu.” ( Davie & Ng, 2013: 7).

Distribution. Known only from Hawaii ( Davie & Ng, 2013).

Figures

Fig. 13. Overall habitus. A, Danarma obtusifrons, male (17.7 × 13.2 mm) (UF-FLMNH 14837), Oahu, Hawaii; B, Danarma silus, holotype male (16.3 × 12.8 mm) (ZRC 2012.0787), Guam; C, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan; D, Danarma garfunkel, holotype male (17.0 × 13.0 mm) (QM), Greta Beach, Christmas Island; E, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; F, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique; G, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; H, Platychirarma buettikoferi, paralectotype male (10.0 × 8.7 mm) (SMF-ZMG 636), Fisherman Lake, Liberia; I, Platychirarma buettikoferi, lectotype male (14.1 × 11.6 mm) (RMNH D 148), Liberia; J, Platychirarma buettikoferi, male (12.6 × 10.4 mm) (ZRC 2015.0298), Cameroon.

Fig. 14. Frontal view of cephalothorax. A, Danarma obtusifrons, male (17.7 × 13.2 mm) (UF-FLMNH 14837), Hawaii; B, Danarma garfunkel, holotype male (17.0 × 13.0 mm) (QM, ex ZRC 2009.0822), Christmas Island; C, D, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan; E, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; F, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique; G, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; H, Platychirarma buettikoferi, paralectotype male (10.0 × 8.7 mm) (SMF-ZMG 636), Fisherman Lake, Liberia.

Fig. 18. Male anterior thoracic sternum and pleon. A, Danarma obtusifrons, male (19.7 × 14.7 mm) (ZRC 2002.0220), Oahu, Hawaii; B, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan; C, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; D, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique; E, Trapezarma angolense, neotype male (39.3 × 32.7 mm) (SMF-ZMG 635), Benguella, Angola; F, Platychirarma buettikoferi, paralectotype male (10.0 × 8.7 mm) (SMF-ZMG 636), Fisherman Lake, Liberia.

Fig. 19. A–C, F–I, Danarma obtusifrons, male (19.7 × 14.7 mm) (ZRC 2002.0220), Oahu, Hawaii; D, E, J–N, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028-002), Lanyu Island, Taiwan. A, left third maxilliped (denuded); B, E, anterior thoracic sternites 1–4; C, D, male pleon; F, J, left G1 (ventral view, denuded); G, K, left G1 (dorsal view, denuded); H, L, left distal part of G1 (ventral view, denuded); I, M, left distal part of G1 (dorsal view, denuded); N, left G2 (denuded). After Davie & Ng (2013: figs. 11, 14). Scales: A–G, J, K, N = 1.0 mm; H, I, L, M = 0.5 mm.

Fig. 43. Vulva. A, Chiromantes haematocheir, female (27.0 × 23.7 mm) (ZRC 2002.0225), Japan; B, Orisarma dehaani, female (20.4 × 17.8 mm) (ZRC 2012.0057), Japan; C, Orisarma intermedium, female (31.8 × 28.4 mm) (ZRC 2013.0140), Japan; D, Orisarma patshuni, female (20.5 × 18.1 mm) (ZRC 2014.0817), Hong Kong; E, Danarma obtusifrons, female (15.7 × 11.6 mm) (UF-FLMNH 14837), Hawaii; F, Danarma eurymerus, paratype ovigerous female (18.0 × 13.4 mm) (ZRC 2012.0956), Taiwan; G, Cristarma eulimene, female (15.6 × 12.8 mm) (ZRC 1968.1.22.3), Mozambique; H, Cristarma ortmanni, female (13.1 × 10.2 mm) (ZRC 2000.1783), Kenya; I, Trapezarma angolense, female (18.2 × 14.3 mm) (ZRC 2015.0297), Cameroon; J, Platychirarma buettikoferi, ovigerous female (11.3 × 9.1 mm) (ZRC 2015.0298), Cameroon.