Parasesarma purpureum n. sp.

(Figs. 13, 14, 19F, 20E, 21F, 22D, 23D, 24E)

Material examined. HOLOTYPE: male (15.9× 13.7 mm) (ZRC 2012.0755 a), Peninsular Malaysia: Tioman Island, 7 July 2012, B.Y. Lee . PARATYPES: 3 males (10.7× 9.2 mm, 13.9×12.0 mm, 15.5× 13.3 mm), 4 females (12.6× 10.7 mm, 13.5×12.0 mm, 14.9× 12.7 mm, 15.6×13.0 mm) (ZRC 2018.0794), same data as holotype. —3 males (11.9×10.0 mm, 12.7× 10.8 mm, 14.2× 12.8 mm), 4 females (10.9×9.0 mm, 12.1× 10.6 mm, 12.6× 10.5 mm, 14.0× 12.2 mm) (ZRC 2018.0795), Peninsular Malaysia: Tioman Island, 4 July 2012, B.Y. Lee. —2 males (11.4×10.0 mm, 11.7× 9.8 mm), 1 female (13.5×11.2) (ZRC 2018.0796), Peninsular Malaysia: Tioman Island, 5 July 2012, B.Y. Lee. —3 males (12.7× 10.8 mm, 13.1× 10.8 mm, 13.1× 10.9 mm), 3 females (12.3× 10.4 mm, 13.6× 11.5 mm, 16.1×14.0 mm) (ZRC 2018.0797), Peninsular Malaysia: Tioman Island, 6 July 2012, B.Y. Lee. —1 male (12.2× 10.5 mm), 1 female (14.5×13.0 mm) (ZRC 2012.0755 b), Peninsular Malaysia: Tioman Island, 7 July 2012, B.Y. Lee. —3 males (15.0× 13.5 mm, 13.4× 11.8 mm, 10.9× 9.8 mm), 2 females (13.9×13.6, 12.3×11.1) (ZRC 2018.0799), Malaysia: Borneo: Sabah, 27 February 2018, J.- J. Li et al.. —1 male (12.6× 11.5 mm), 1 female (15.4× 13.8 mm) (MZB Cru 4800), Malaysia: Borneo: Sabah, 27 February 2018, J.- J. Li et al.. — 1 male (13.7× 12.4 mm) (NMNS-7779-027), Malaysia: Borneo: Sabah, 27 February 2018, J.- J. Li et al.. — 2 males (14.5×13.0 mm, 14.3× 13.4 mm) (NMCR 50704), Malaysia: Borneo: Sabah, 27 February 2018, J.- J. Li et al..

Diagnosis. Carapace (Figs. 13A, E, 14A, 22D) squarish in general outline, 1.2 times broader than long; regions well defined, separated by shallow grooves; postfrontal region distinct, separated into 4 lobes by deep grooves; front deflexed downwards (Figs. 13C, D) margin slightly concave in dorsal view; lateral margin straight, subparallel along most of length before curving to join almost straight posterior carapace margin; cornea extending or just reaching tip of external orbital tooth (Figs. 13A, E, 14A, 22D). Ischium of third maxilliped with shallow median sulcus, merus with distinct submedian ridge; exopod slender, tip reaching half-length of outer margin of merus, flagellum long. Male cheliped palm with 2 transverse pectinate crests (12 and 7 corneous teeth, respectively) on upper surface; upper surface of dactylus with 9 or 10 symmetrical, obliquely elongate dactylar tubercles, proximal tubercles steep, sharp, the others tubercles large, distalmost tubercle indistinct (Figs. 14C, D, 19F). Ambulatory legs relatively slender for this species-complex, P3 and P4 about 1.6 times carapace width; P3 and P4 coxae without dense setae; P3 merus 2.6 times as long as broad; P3 propodus 4.4 times as long as broad; P3 dactylus 0.4 times length of propodus (Fig. 20E). G1 relatively stout (Figs. 14E–H, 21F,); apical process corneous, short, bent at angle of 45°, long, stout, ending in rounded tip. G2 longer than quarter length of G1 (Fig. 21F).

Colour in life. Carapace dark brown, fingers of chelipeds are pale white, ambulatory legs violet or purplish brown. (Fig. 22D, 23D, 24E).

Remarks. Parasesarma purpureum n. sp., is most similar to P. kui n. sp. (from Taiwan) with regards to its relatively broader carapace. However, the following differences are observed; the carapace surface of P. purpureum has scattered tufts of short setae, the dactylar tubercles of the male chela are consistently nine in number (Figs. 14D, 19F,); the corneous tip of the G1 is proportionately broader (Figs. 14E–H); and the general colour in life is dark purple, or brownish-purplish with white chelae (Figs. 22D, 23D). By contrast, in P. kui n. sp., the carapace surface is glabrous; the dactylar tubercles are nine or ten (Figs. 10C, D, 19D); the corneous tip of the G1 is proportionately narrower (Figs. 10E–H), and in life, the colour of the carapace is black or light brown, with the chelae possessing orange fingers (Figs. 22C, 23C).

Etymology. From the Latin purpureum for “purple” with reference to the general colour of the new species.

Distribution. So far known from Tioman Island, Peninsular Malaysia; and Sabah, East Malaysia, Borneo.

Ecology. Parasesarma purpureum n. sp. in Malaysia (Tioman Island and Sabah) is often observed at night and climbing on mangrove tree trunks and aerial roots above the water level.