Pleistacantha griffini Ahyong and Lee, 2006

(Fig. 5A)

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 28 (Timor Sea; 09°34.4′S, 128°06.0′E – 09°33.5′S, 128°03.4′E, 295–296 m depth); 3 m beam trawl; June 24, 1972; 1 ♂ (NSMT-Cr 29258: CL 10.2 mm excluding pseudorostral spines, CB 6.7 mm).

Remarks. The general appearance of species of Pleistacantha changes somewhat owing to sizerelated inflation of the branchial regions and to sexual dimorphism (e.g. Prema et al., 2020). In addition, as briefly discussed by Ahyong and Lee (2006), the distinctness of sexual dimorphism probably varies among species. The taxonomy is, therefore, usually discussed mainly on the basis of adult specimens. The present specimen, a juvenile male with poorly developed gonopods, nevertheless possesses diagnostic features of P. griffini, described from the North West Shelf, Western Australia (Ahyong and Lee, 2006).

Pleistacantha griffini closely resembles P. moseleyi (Miers, 1886) from the Philippines (Ahyong and Lee, 2006), and of five features discussed by Ahyong and Lee (2006), the followings are available to distinguish the two species (see also Ng et al., 2017, figs. 3A, 4A, 5A, 6A–B, 7A–C, 8A–B, 9A–B, 10A–D). The mesial margins of the branchial regions are more widely separated such that several rows of small spines are present along the midline between the two regions in P. griffini (a single row of spines in P. moseleyi); and the merus of the fifth ambulatory leg is relatively shorter in P. griffini than in P. moseleyi (merus length/pcl: 0.7 in P. griffini; 0.8–1.0 in P. moseleyi; 0.6 in the present male).

Distribution. North West Shelf of Australia; Timor Sea; Sumatra and off the Tanimbar Islands, Indonesia; 295–400 m depth.