Potamiscus annandalii Alcock, 1909

Ng, Peter K. L. & Yeo, Darren C. J., 2023, Clarifying the identities of the Asian potamid genera Potamiscus Alcock, 1909, Ranguna Bott, 1966, and Dromothelphusa Naiyanetr, 1992 (Crustacea: Brachyura: Potamoidea), Raffles Bulletin of Zoology 71, pp. 632-657 : 636-640

publication ID	https://doi.org/ 10.26107/RBZ-2023-0048
publication LSID	lsid:zoobank.org:pub:19D286F4-F712-4645-93FF-1AC19A55EDE9
persistent identifier	https://treatment.plazi.org/id/882487B0-FFFE-FFE5-F6F3-F961EF31F826
treatment provided by	Felipe
scientific name	Potamiscus annandalii Alcock, 1909
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Treatment

Potamiscus annandalii Alcock, 1909 View in CoL

( Figs. 1–4 View Fig View Fig View Fig View Fig )

Potamiscus annandalii Alcock, 1909: 246 View in CoL .

Potamon (Potamiscus) annandalii – Alcock, 1910b: 57, pl. 3 fig. 10.

Potamiscus annandalii View in CoL – Bott, 1970: 158, pl. 38 fig. 28, pl. 46 fig. 26; Brandis, 2000: 63, pl. 2a–c; Yeo & Ng, 2007: 293, fig. 11; Ng et al., 2008: 165; Cumberlidge et al., 2009: supplementary table.

Material examined. Lectotype: male (33.0 × 25.0 mm) ( ZSIK 6602-3 /9), Nemotha, Cachar, coll. J. Wood-Mason,

no date. Paralectotypes: 2 males (larger 30.5 × 23.6 mm), 3 females (largest 33 mm damaged; larger intact 28.2 × 22.1 mm) ( ZSIK 6602-3 /9) , 1 male (33.7 × 25.3 mm), 1 female (28.2 × 21.8 mm) ( ZSIK 6595-6 /9), same data as lectotype ; 1 male (30.5 × 25.7 mm), 1 female (30.0 × 23.1 mm) ( NHM 1909.9.2.5), same data as lectotype, presented by Indian Museum .

Diagnosis. As for genus.

Description of lectotype and paralectotype males. Carapace broader than long, relatively high, dorsal surface distinctly convex transversely and longitudinally in frontal view; epigastric cristae well developed, separated by distinct groove opening up into long inverted V-shape posteriorly, slightly anterior to postorbital cristae, more or less confluent with postorbital cristae, faintly separated by short, indistinct groove; postorbital cristae strong, sharp, almost confluent with epibranchial tooth; frontal and postorbital areas not compressed, with these regions relatively wide in dorsal view ( Figs. 1A View Fig , 2A, B View Fig ); regions behind epigastric and postorbital cristae almost smooth; pterygostomial, sub-hepatic, suborbital and sub-branchial regions covered with small scattered granules to almost smooth; cervical groove distinct, posteriorly joining H-shaped gastric grooves ( Figs. 1A View Fig , 2A, B View Fig ). Frontal margin appears almost entire, straight; gently deflexed downwards ( Fig. 2A, B, D View Fig ). External orbital angle triangular, outer margin longer than inner margin; epibranchial tooth low but distinct, separated by clear cleft; anterolateral margins cristate, serrated, gently convex, not confluent with posterolateral margin; posterolateral margins gently converging posteriorly; posterior carapace margin gently sinuous ( Figs. 1A View Fig , 2A, B View Fig ); branchial regions gently rugose; metabranchial region rugose ( Figs. 1A View Fig , 2A, B View Fig ). Orbits large, slightly oblique in position; supraorbital margin gently sinuous, cristate; eyes large, almost occupying orbit, peduncle short, stout; cornea large ( Fig. 5B View Fig ). Antennular fossae longitudinally narrow, slit-like ( Figs. 1B View Fig , 2D View Fig ); antenna small, flagellum not extending beyond orbit ( Figs. 1B View Fig , 2D View Fig ). Epistome posterior margin with distinctly triangular median tooth, outer part strongly sinuous ( Figs. 1B View Fig , 2D, F View Fig ). Endostome smooth, no clear ridge visible.

Third maxilliped with surface glabrous, inner margin lined with short setae; merus subquadrate, ca. half of ischium length, anteroexternal angle rounded; median part gently depressed; ischium relatively short, broadly rectangular, with shallow oblique median sulcus; exopod slender, long, distal part exceeding distal edge of ischium, reaching one third length of merus, flagellum vestigial or absent ( Fig. 2C View Fig ).

Chelipeds stout, nor elongate, heterochelous [in paralectotype male] ( Figs. 1A View Fig , 2A View Fig , 3A View Fig ); outer surfaces with well-spaced large acute tubercles; margins of merus lined with tubercles, without obvious subterminal spine, outer surface rugose ( Fig. 5H View Fig ); carpus margins appear uneven, inner distal angle with large, subdistal spine and basal tubercle ( Fig. 5I View Fig ); fingers subequal in length to palm, dorsal and ventral margins with large sharp tubercles; cutting edges of fingers with strong cutting teeth ( Figs. 1A View Fig , 2A View Fig , 3A View Fig ).

Ambulatory legs not elongate, stout, glabrous; merus subdistal spine absent, upper margin weakly serrated; propodus relatively long; dactylus longer than propodus, slender ( Fig. 2A View Fig ).

Anterior thoracic sternites relatively narrow transversely, surface smooth, glabrous; suture between anterior thoracic sternites 2 and 3 distinct, complete, reaching edge of sternum; no obvious suture between anterior thoracic sternites 3 and 4; sternopleonal cavity reaching imaginary line joining posterior edge of cheliped bases; tubercle of male press-button locking mechanism small, on posterior third of thoracic sternite 5 ( Figs. 1C, D View Fig , 2G View Fig , 3E View Fig ).

Male pleon broadly triangular, all somites and telson free; somites 3–5 trapezoidal, lateral margins almost straight to gently convex; somite 6 conspicuously wide, lateral margins gently convex; telson triangular with almost straight lateral margins, as long as somite 6 ( Figs. 1C View Fig , 2G View Fig , 3B View Fig ).

G1 relatively stout; terminal and subterminal segments clearly demarcated; subterminal segment stout, not neck-like distally, without shelf on upper part of outer margin; terminal segment distinctly bent outwards, conical, distally tapered, without any trace of dorsal flap, less than one third length of subterminal segment, without trace of dorsal flap, without longitudinal torque, without swelling on inner margin, groove for G2 marginal ( Figs. 1E, F View Fig , 3C View Fig , 4A–D View Fig ). G2 longer than G1; distal segment longer than half length of basal segment; basal segment relatively wide, with outer margin convex ( Figs. 1G View Fig , 3D View Fig , 4E View Fig ).

Female and variation. Female pleon ovate, covering most of thoracic sternum. Vulva large, occupying ⅔ anterior part of thoracic sternite 6, touching suture between thoracic sternites 5 and 6, operculum present, sternal vulvar cover on posterior margin, opening obliquely inwards ( Fig. 3F View Fig ).

Remarks. Alcock (1909: 246) described the species from nine males and six females collected in Nemotha, Cachar, northern India. Bott (1970: 159, pl. 46) designated a male specimen measuring 34.0 × 26.0 mm from ZSIK 6602-3/9 as the lectotype of the species. This specimen was examined ( Fig. 1 View Fig ), and although it is in relatively poorly condition, most of the key characters are intact. Brandis (2000: fig. 2a–c) subsequently examined and illustrated a syntype male (it should be one of the paralectotypes) of the species; the specimen and the paralectotype female are re-examined here ( Figs. 2–4 View Fig View Fig View Fig ).