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Wu, Yu & Ng, 1999

Description (male holotype): Carapace longitudinally ovate, ratio of cw to pcl 0.83; dorsal surface smooth, covered with very low, felt-like pubescence. Rostral spines slightly deflexed downwards; relatively long (rl 0.24 times pcl); with broad base, tapering gradually to blunt tip, tip with tuft of setae; proximal dorsal surface with longitudinal tuft of hooked setae. Orbital eave relatively expanded; preorbital tooth triangular, directed obliquely outwards, tip with tuft of hooked setae; lateral margin concave, with small swelling behind eye. Eyestalks short, relatively slender, cornea terminal; eave completely covering eye when apposed against carapace.
Hepatic margin produced into triangular, flat, broad, sublamelliform lobe with blunt tip; length about two-thirds base; inner and posterior margins almost straight, anterior margin about two-thirds length of posterior margin; posterior margin clearly divergent from midline of carapace. Branchial margin with two relatively large, triangular, outwardly directed lobes on posterior part which are about half the size of the hepatic lobe, tips of both lobes blunt, with short, hooked setae, last lobe smaller than preceeding one; anterior part of margin with low but distinct swelling. Lateral carapace margin with weak, very low ridge. Posterior carapace margin strongly convex. Gastric regions weakly elevated; protogastric region with low, rounded tubercle opposite anterior part of hepatic lobe, highest point with tuft of very short, stiff setae; mesogastric tubercle low, rounded, glabrous, with tuft of very short, stiff setae. Cardiac region weakly elevated, with small, low median tubercle. Intestinal region with low median, rounded tubercle. Pterygostomial region with low, rounded tubercle on distal half.
Third maxilliped smooth; basis and ischium separated by suture along inner part only; ischium subrectangular, with shallow median depression, antero-internal angle produced slightly, inner margin serrated with blunt teeth; merus with shallow median depression, antero-external angle produced to rounded lobe; exopod stout, basal two-thirds subrectangular with gently concave outer margin which is subparallel with lateral margins of ischium, distal one-third triangular with lateral margin deeply concave, tip not reaching upper edge of merus. Basal antennal article smooth, proximal part with shallow but distinct depression; basal part broad, narrowing gradually; distal part without antero-lateral projection.
Chelipeds elongate, subequal; about 2.0 times postrostral length. Chelae swollen, smooth; fingers 0.6 times length of palm, medially gaping when fingers closed, tips gently curved inwards, inside surface sub-spatuliform; cutting edge of dactylus with low median, submolariform tooth, distal one-third with blunt teeth; proximal two-thirds of cutting edge of pollex smooth, distal one-third with blunt teeth; distal part of cutting edges (especially near tip) not pigmented. Merus smooth with 2 blunt dorsal distal and 1 outer marginal tubercles, tips with short, stiff setae. Carpus with very low, blunt ridge along outer-dorsal surface.
Ambulatory legs smooth, first leg longest, approximately 1.5 times postrostral carapace length, fourth leg shortest, approximately 0.91 times postrostral carapace length. Merus of first leg with 1 proximal and 1 median seta along dorsal margin; with rounded dorsal distal tubercle, tip with several setae; meri of other legs with rounded dorsal distal tubercle tipped with one or two setae, dorsal margin with a median to submedian seta. Carpus with very low median longitudinal ridge on outer surface of first to third legs. Propodus with broadly triangular median lobe on ventral margin; distal margin lined with long, stiff setae; forming subchelate structure with dactylus. Dactylus gently hooked; inner margin with two rows of about ten short, stout spines along each row, with stiff setae along proximal two-thirds.
Anterior thoracic sternum smooth, all sternites fused without trace of sutures; two small, circular submedian pits on sternite 2, separated by low, rounded longitudinal ridge; sternite 3 with two broad depressions separated by low, rounded longitudinal ridge; sternite 4 with shallow median depression just anterior to abdominal cavity.
Abdomen triangular. Telson triangular, lateral margins gently concave. Segment 6 squarish, lateral margins distinctly concave. Segments 3-5 fused, immovable, but sutures visible, with lateral parts deeper and more distinct, segments 5 to 3 progressively more trapezoidal and shorter. Segment 2 trapezoidal, lateral margins convex. Segment 1 dumb-bell-shaped, lateral margins almost straight.
Male first pleopod with distal one-third gently curving outwards; distalmost part gently bent outwards, dorsal fold (inner-distal margin) low, tip relatively sharp. Male second pleopod relatively short, 0.31 times length of male first pleopod, distal part spatuliform.
Females: Adult females resemble male holotype except that the rostrum is slightly shorter (rl 0.18-0.24 (mean 0.21) times pcl), chelipeds very slender, not elongate; chelae not inflated, fingers straight (not gaping when closed) and cutting edges lined throughout with uniformly-sized small teeth. Adult female abdomen surface smooth, segments 3-6 fused, sutures not visible; telson semicircular. Vulva slit-like, set at oblique angle. In two subadult females (12.5 and 13.0 mm pcl; ZRC 1998. 32-33), abdomen rounded but not swollen, pleopods not fully setose. (Wu et al., 1999)

Type locality: Chenauo, Taipei County, Taiwan.
Range: Taiwan - Taipei County (Wu et al., 1999).

Acanthonyx formosa