Danarma, Schubart & Ng, 2020

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 : 920-921

Danarma , new genus

Type species. Sesarma obtusifrons Dana, 1851 , by present designation. Gender neuter.

Diagnosis. Carapace ovate-trapezoidal, broader than long; frontal margin entire, prominently deflexed, almost completely shielding antennules from frontal view, margin much longer than posterior carapace margin; lateral margins of carapace entire, posterolateral part distinctly converging; regions of carapace poorly demarcated; postfrontal and epigastric crests separated by relatively deep grooves, margin relatively rounded, regions clearly separated; basal articles of antenna and antennules separated by septum; dorsal margin of palm smooth; outer surface of palm smooth, inner surface with prominent transverse submedian swelling, highest point with transverse ridge of granules, outer surface of palm and pollex convex, outer lower surface of palm smooth; dorsal margin of chelipedal dactylus smooth; inner distal margin of merus of cheliped not lamelliform; inner surfaces of first to third ambulatory coxae with numerous long setae between them; male thoracic sternites 2–4 relatively narrow in adults, suture between sternites 3 and 4 distinct; male sternopleonal cavity reaching two-thirds length of sternite 4 to just before anterior margin of sternite 2; male thoracic sternite 5 smooth, without depression on anterior part; G1 slender or relatively stout, chitinous part short or relatively long. Vulva on anterior part of sternite 6, anterior edge presses against sternite 5; anterior and posterior sternal vulvar covers flat, triangular, tips overlapping; opening not projecting, below sternal vulvar covers.

Etymology. The genus name is derived from James D. Dana (1813–1895), who described the type species, in arbritary combination with the genus name Sesarma . The gender is neuter.

Included species. Sesarma obtusifrons Dana, 1851 ; Chiromantes silus Davie & Ng, 2013 ; Chiromantes leptomerus Davie & Ng, 2013 Chiromantes eurymerus Davie & Ng, 2013 ; Chiromantes garfunkel Davie & Ng, 2013 .

Remarks. As discussed earlier, what used to be called Chiromantes obtusifrons is now a group of five species ( Davie & Ng, 2013), all sharing a peculiar frontal margin that is very broad and prominently bent downwards such that much of the antennae and antennules are completely covered in frontal view. The broad front also results in a pecular carapace shape—clearly trapezoidal with the posterolateral margins strongly converging towards the posterior carapace margin, but with the lateral margins arcuate, resulting in a transversely subovate form ( Figs. 13A–D , 14A–D ). The outer surface of the palm is also smooth, with no longitudinal ridge, the dactylar finger completely unarmed on the dorsal margin ( Fig. 15A, B ), and the surfaces between the first to third ambulatory coxae have distinct dense tufts of long setae ( Fig. 18A, B ). The presence of strongly setose ambulatory coxae is a feature shared with species of Cristarma , new genus, from East Africa (see later). This suite of distinctive characters shared by five similar species is strong support for the establishment of a new genus, here named Danarma .

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. 15. Chela. A, B, Danarma eurymerus, holotype male (18.7 × 14.8 mm) (NMNS-7028–002), Lanyu Island, Taiwan; C, D, Cristarma eulimene, male (22.2 × 17.2 mm) (ZRC 1968.1.22.2), Inhaca Island, Mozambique; E, F, Cristarma ortmanni, male (20.0 × 15.5 mm) (ZRC 1968.1.22.1), Inhaca Island, Mozambique. A, C, E, outer view; B, inner view; D, F, dorso-lateral view showing pectinated ridge on palm.

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.