Scandarma papua, Naruse & Ng, 2020

Naruse, Tohru & Ng, Peter K. L., 2020, Revision of the sesarmid crab genera Labuanium Serène and Soh, 1970, Scandarma Schubart, Liu and Cuesta, 2003 and Namlacium Serène and Soh, 1970 (Crustacea: Decapoda: Brachyura: Sesarmidae), with descriptions of four new genera and two new species, Journal of Natural History (J. Nat. Hist.) 54 (7 - 8), pp. 445-532 : 488-491

Scandarma papua sp. nov.

( Figures 23 , 24 )

Material examined

Holotype. UF2335 , male, 15.8 × 17.8 mm, Louisiade Archipelago , Milne Bay Province, Papua New Guinea, coll. G. Paulay, 4 June 1998.

Others. NHM 1922.11.9.2–5, 1 male, 14.5 × 16.1 mm, 1 female, 11.3 × 12.8 mm, Gabmetzung , Markham River, Huon Gulf, Papua New Guinea, coll. W.J. Potter; RMNH. CRUS.D. 45517, 1 male, 15.4 × 16.7 mm, Hollandia , Papua New Guinea, coll. G. van Hout, May–June 1955 .

Diagnosis

Carapace subsquarish, external orbital angle sharp, lateral margins slightly divergent posteriorly; 2 pairs of postfrontal lobes present, lateral lobes slightly exceeding mesial lobes anteriorly in adults ( Figure 23 (a)); anterior margins of all lobes relatively close to but never reaching frontal margin in dorsal view. Palm ( Figure 23 (b,c)) of male chela swollen; outer surface granulated, granules smaller on lower part, with weak protuberance on proximal part of smooth sloping area around bases of fingers; upper surface ( Figure 23 (c)) with 1 straight, longitudinally traversing row of densely packed small granules, and with several short, oblique rows on inner side. Immovable finger ( Figure 23 (b)) almost straight, gradually tapering towards tip; occlusal margin lacking marked proximal elevation, lined with small teeth on proximal two-fifths, 1 large bifid tooth submedially, followed distally by 4 or 5 smaller teeth, subdistally with 1 large tooth; lower margin of immovable finger irregularly lined with small teeth. Movable finger ( Figure 23 (b)) gently curved, occlusal margin with 2 large teeth on proximal third, followed distally by smaller teeth, and 1 subdistal tooth; inner side of upper surface of movable finger with regular row of flat, rounded granules, granules becoming smaller proximally and distally. Subdistal tooth of immovable finger fitting between tip and subdistal tooth of movable finger when closed. Male pleonal somite 3 widest, somite 4 abruptly narrowed distally, lateral margins of somites 3–5 clearly concave ( Figure 24 (a)). G1 ( Figure 24 (b)) short, almost straight, stout, narrowed medially, distal end with anterolaterally directed wide corneous process. Vulvae ( Figure 24 (c)) located on distal two-fifths of sternite 6, anterior margin adjacent to thoracic sternal suture 5/6 ellipsoidal, rimmed except for posteromesial corner and mesial margin, mesial end of posterior rim produced to wide, short triangular lobe, similar triangular lobe present mesially; sternal vulval cover developed from anterolateral margin, covering vulva except for mesial quarter, cover produced ventrally as trigonal pyramid structure.

Variations

In small individuals (e.g. CW 12.8 mm), all postfrontal lobes are aligned anteriorly; lobes relatively close to but never reaching frontal margin in dorsal view ( Figure 17 (c)); there are a clearly discernible epibranchial teeth on the anterolateral margin of the carapace; ambulatory legs are proportionally wider, especially on meri. Small females, however, already have a row of granules on the upper surface of the palm and granules on the upper margin of dactylus, indicating that adult females also have such a row of granules.

Colouration

Live colouration not known.

Distribution

New Guinea: Louisiade Archipelago , Milne Bay Province [type locality]; Gabmetzung, Markham River, Huon Gulf; Jayapura (as Hollandia) (present study).

Etymology

The species name is derived from its known distributional area. The name is used as a noun in apposition.

Remarks

Scandarma papua sp. nov. superficially resembles Sc. gracilipes s.s., but the two species can be distinguished from each other by a number of characters of the male chela, ambulatory legs, vulva, male pleon and G1 ( Table 3 ).

Figures

Figure 17. Dorsal view of carapace of small individuals of Scandarma species. a, Sc. lintou, RUMF-ZC -2024, female, 12.9 × 13.6 mm; b, Sc. gracilipes, RUMF-ZC-5014, female,11.2 × 12.0 mm; c, Sc. papua, NHM 1922.11.9.2–5, female, 11.3 × 12.8 mm.

Figure 23. Scandarma papua sp. nov. Holotype,UF2335, male, 15.8 × 17.8 mm (Louisiade Archipelago, Papua New Guinea). a, habitus, dorsal view; b, right chela, outer view; c, right chela, upper view.

Figure 24. Scandarma papua sp. nov. a, b, RMNH.CRUS.D. 45517, male, 15.4 × 16.7 mm (Hollandia, Papua New Guinea); c, NHM 1922.11.9.2–5, female, 11.3 × 12.8 mm (Huon Gulf, Papua New Guinea). a, pleon; b, right G1, ventral view; c, right vulva. Scale bars: a= 5 mm; b, c= 1 mm.