Prismatopus albanyensis Ward, 1933

Manikandan, K, Megalaa, N, Valliappan, Subramanian, Nandini, K, Rani, Lourdu V, Dakshinamurthi, Senthil & Nagappan, Nagappan, 2022, Crabs (Crustacea, Decapoda) from the Seas of East and Southeast Asia Collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 3. Sahul Shelf, Bulletin of the National Museum of Nature and Science. Series A, Zoology 48 (2), pp. 35-83 : 52-57

Prismatopus albanyensis Ward, 1933 ( Figs. 8A, 9A–C, 10A–B, 11D ·E)

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 29, 1Ə ( CB 10.2 mm excluding branchial spines× PCL 14.9 mm), NSMT-Cr 30726. — Sta. 30, 1 Ə (CL 12.8× CB 8.4 mm), NSMT-Cr 30727.

Description. Carapace ( Figs. 8A, 9A) 1.5 times as long as wide, weakly constricted behind hepatic regions; surface covered sparsely with curled setae. Pseudorostrum divergent anteriorly, with angle of 50–70°; pseudorostral horns gently curved laterally, 0.4 times as long as PCL, almost straight in lateral view. Frontal region with deep, narrow, longitudinal groove running from anterior gastric slope toward pseudorostral divergence between 2 blunt longitudinal ridges. Supraorbital eave not markedly expanded; first preorbital lobes absent; second preorbital lobes gently curved dorsally, broadly U-shaped in frontal view, knobbed apically, distal end armed with spinules, anterior margin with 1 or 2 acute spinules on midlength, posterior margin subproxi- mally lined with 3 or 4 spinules; antorbital lobe broad, lamellar, gently curled dorsoanteriorly; intercalate lobe subrectangular, digitated on both margins; postocular lobe as long as or slightly longer than hepatic projection, with obtuse tooth on posterior margin. Eyestalk slender, cornea ventrally, shorter than half length of stalk. Gastric region weakly elevated, armed with 2 subequal, knobbed spines arranged longitudinally, posterior slope smooth ( Figs. 8A, 9A–B). Hepatic region weakly inflated, anterolaterally sloped, terminated with triangular tooth followed posterolaterally with 1 or 2 additional teeth ( Figs. 8A, 9A). Branchial region ( Figs. 8A, 9A–C) armed dorsolaterally with 2 long, knobbed spines, anterior dorsolateral margin not defined, subsurface bearing 2 low tubercles, branchial submargin, posterior carapace margin finely spi- nulate. Cardiac region weakly elevated, mounted with 2 knobbed spines side by side; both spines raised at fused bases, as high as gastric spines ( Figs. 8A, 9A–C). Intestinal region smooth, with short spine just above posterior carapace margin ( Figs. 8A, 9A–B).

Basal antennal article ( Fig. 10A) narrow, lateral margin broadly concave; distolateral angle produced into moderately long, blunt, triangular lobe, directed laterally or slightly posterolaterally, subrectangular in frontal view; proximolat- eral angle produced into low, round lobe; mesial margin ridged, bearing broad, low, erect, triangular tooth, distomesial angle produced ventrally into rectangular lobe, similar in size, shape to distolateral spine (in frontal view); proximome- sial lobe rounded, continuous with anterolateral angle of epistome. Distal 2 peduncular articles free; penultimate article as long as ultimate article. Flagellum exceeding tip of pseudorostral horn.

Antennular peduncular first article medially ridged, with 2 small spines longitudinally, with strong, triangular spine sublaterally. Inter-antennular septum large, subacute, triangular, tip pointing slightly anteriorly.

Pterygostomian region weakly inflated, gener- ally smooth, sharply ridged, bearing sharp, ventrally erected, triangular teeth.

Third maxilliped surface smooth under microscopy. Mesial two-thirds of ischium distinctly depressed, separated from lateral part by sharply crested, longitudinal ridge, anteromesial lobe, weakly produced anteriorly, firmly fitted in sharply rimmed, posteromesial concavity of merus (when closed). Merus dilated distolaterally, distomesial, distolateral margins upturned, depressed, proximolateral lobe depressed. Carpus short, entire, external surface depressed, lateral margin sharply defined, round. Propodus rectan- gular, extensor margin sharply defined. Dactylus finger-like, as long as propodus.

Chelipeds subequal in length, shape. Ischium not markedly inflated, armed proximally with broad, low triangular teeth, distally with 2 lamellar lobes. Merus trigonal, dorsally armed with 3, broad, ventrally with 3 triangular teeth; medial knob at articulation with carpus compressed into large subspatulate, triangular teeth. Carpus not markedly inflated, outer margin sharply carinate, entire, dorsal surface with sharp rectangular carina, inner margin irregularly dentate, with small subproximal spine, ventral surface unarmed. Propodus not markedly inflated, upper margin sharply crested, lower margin obtusely defined. Fingers narrowly gaping in proximal half, finely toothed on both cutting margins, dac- tylus marked with broad, low, triangular tooth (adolescent male, PCL 12.8 mm), widely gaping, toothed in distal half, contiguous in distal one-third, subproximal tooth on dactylus simple or bifid, larger than counterpart on immovable fin- ger (full-grown male, PCL 14.9 mm).

Ambulatory legs (P2–5) slightly decreasing in length posteriorly, extensor, flexor surfaces bear- ing rows of strongly curled setae, long, simple setae. Basis-ischium marked with strong, triangular, subdistal tooth. Merus trigonal, extensor, flexor margins armed with small spines, distolat- eral, median knobs at articulation with carpus prominent, elongated into knobbed spine (distolateral spine sometimes lobate, shorter than median spine). Carpus prismatic, elongate, triangular, dorso-extensor margin weakly tuberculate, ventro-extensor margin armed with 4 teeth each bearing long, simple seta. Propodus prismatic, lateral surfaces lined with long, simple setae. Dactylus slender, gently curved in distal half, extensor margin arranged with row of long setae.

Thoracic sternites generally smooth, with distinct sutures on sternites 5–8. Sterno-pleonal cavity sharply rimmed, continuous with erected, triangular tooth on both sides, separating sternites 1–4 from sternite 5.

Pleon ( Fig. 10B) with 6 somites and telson; distal 5 somites 1.3 times longer than proximal width, somites 2–6 weakly elevated medially, anterior end produced into small tubercle mounted with few simple setae in somites 3–5. Somite 1 short, narrow, anterolateral lobe rounded, upturned. Somite 2 divergent anteriorly, lateral margin bilobed. Somite 3 subrhomboid, strongly elevated on both lateral parts, lateral margin arcuate. Somite 4 rhomboid, lateral margins convergent. Somite 5 rhomboid, lateral margins slightly convergent. Somite 6 rectangular, lateral margin weakly convex on midlength. Tel- son ( Fig. 10A) subtriangular, lateral margin straight.

G1 shaft ( Fig. 11D) almost straight, distal onefifth teardrop-shaped, proximally with cluster of long spines, tip acuminate, lateral margin lined with stiff setae in distal one-third; subapical flap simple, not markedly twisted. G2 shaft short, slightly curved, with small, conical apical process ( Fig. 11E).

Remarks. In the revision of the genus Acan- thophrys A. Milne-Edwards, 1865, Griffin and Tranter (1986) established a new genus Tha- canophrys. Later, Ng et al. (2001) showed that the genus Prismatopus Ward, 1933 , has nomenclatural priority over Thacanophrys . Of the 12 species in the genus Prismatopus , P. albanyuensis is characteristic in having a combination of the lamellar preorbital and antorbital spines, and a strong spine on the carapace posterior margin. The present specimens agree with the original description by Ward (1933), and also with Chlorinoides barunai Serène, 1969 , which was synonymized with this species by Griffin and Tranter (1986).

Distribution. Known from the Albany Passage, northern Queensland, 16–21 m depth (type locality), and otherwise from some localities in the Arafura Sea, 25–57 m depth.