Aniptumnus vietnamicus, Ng & Clark, 2008

Ng, Peter K. L. & Clark, Paul F., 2008, A revision of Latopilumnus Türkay & Schuhmacher, 1985, and Aniptumnus Ng, 2002 (Crustacea: Decapoda: Brachyura: Pilumnidae) with larval comparisons, Journal of Natural History 42 (9 - 12), pp. 885-912 : 904-909

Aniptumnus vietnamicus new species

( Figures 19–21 )

Material examined

Nhatrang Bay , Vietnam, coll. R. Serène, 10 April 1966. Holotype, „ (7.9× 5.7 mm), ZRC 1970.1 .10.1. Paratypes; 1 ♀ (8.8× 6.5 mm), ZRC 1970.1.10.2; 1 „ (8.8× 6.9 mm), MNHN B-21631, 1 „ (8.6× 6.5 mm), MNHN B-20982, 1 ♀ (6.2× 4.1 mm), 1 ovig. ♀ (4.9× 3.3 mm), MNHN B-21632 .

Description of male holotype

Carapace transversely hexagonal, broader than long, regions defined by broad, shallow grooves, surface mostly smooth except for patches of small rounded granules on parts of gastric and branchial regions, most of surface visible, setae sparse, aggregated mainly around granular areas. Frontal margin with two lobes, separated by broad V-shaped notch medially, margin gently convex, lined with small granules, with row of short sparse setae just behind margin; lateral frontal lobe very low but discernible, separated from frontal lobe by shallow concavity, separated from supraorbital margin by right angled junction. Supraorbital margin distinctly granulated, entire. Entire anterolateral margin granulated, edges with sparse setae; external orbital angle low, not prominently projecting; rest of anterolateral margin with 3 well-defined teeth; first tooth broadest, most prominent. Posterolateral margin almost straight to slightly sinuous, converging towards gently convex posterior carapace margin. Basal antennal segment subrectangular, filling orbital hiatus. Orbits transverse; eyes large, filling entire orbital space; distal part of ocular peduncle covered with small granules. Infraorbital margin distinctly granulated, submedian part projecting anteriorly as triangular tooth, visible from dorsal view. Suborbital, sub-branchial and pterygostomial regions granular. Merus of third maxilliped squarish, anterolateral angle not prominently produced, surface granular, especially along margins, inner margin granular; ischium subrectangular, with very shallow submedian sulcus; exopod stout, distal edge almost reaching anterior edge of merus, inner subdistal tooth low, with well developed flagellum.

Chelipeds subequal, right larger. Inner margin of fused basis-ichium with several large and small granules. Inner margin of merus with numerous small granules. Outer surface of carpus with numerous rounded granules, with scattered setae that do not obscure surface, inner distal angle produced as distinct tooth, lined with large tubercles. Outer surface of larger palm evenly covered with similar-sized granules; fingers distinctly shorter than palm; outer surface of pollex with distinct longitudinal groove on subventral surface; cutting edges with basal teeth proportionately larger but not molariform. Outer surface of smaller chela with evenly-sized granules all over; fingers shorter than palm; outer surface of pollex with deep submedian longitudinal groove, cutting edges with several teeth.

Ambulatory legs covered with scattered setae, especially on carpus and propodus; second leg longest. Distal margin of basis-ischium lined with prominent granules, comb-like, most distinct on fourth leg. Dorsal margin of first to third meri granular, gently serrated; proximal part of ventral margins with scattered granules. Dorsal margin of fourth merus serrated, proximal half of ventral margin lined with distinct short spines and granules. Carpus unarmed. Dactylus gently curved with sharply tapering tip.

Surfaces of anterior thoracic sternites smooth, covered with very short pubescence. Sternites 2 and 3 separated by gently curved groove; sternites 3 and 4 fused, demarcated only laterally by notches. Male abdomen with all segments freely articulating, surfaces almost smooth. Telson triangular with tip rounded. G1 strongly sinuous, distal part distinctly recurved from ventral view. G2 very short, sigmoid.

Etymology

The species is named after its country of origin, Vietnam.

Remarks

All the specimens of the present new species had been collected from Vietnam and identified by the late Raoul Serène as ‘‘ Parapilumnus malardi ’’. Direct comparisons of the material, however, reveal numerous differences that indicate that Vietnamese material is not conspecific, or even congeneric with what is here defined as L. malardi , new combination. The form of the last (fourth) ambulatory leg in particular is diagnostic for Aniptumnus , with the distal margin of the basis-ischium lined with comb-like granules and the proximo-ventral margin of the merus distinctly granulated ( Ng 2002). The form of the G1 of A. vietnamicus is typical of many pilumnids and the distalmost part is not truncated. Aniptumnus vietnamicus , new species, also differs from L. malardi , new combination, in having more prominent anterolateral teeth, the carapace gastric and branchial regions having distinct patches of small granules (sparse to absent in L. malardi , new combination), and the outer surfaces of the pollex of both chelae are smooth (with a prominent median longitudinal row of granules in L. malardi , new combination).

Aniptumnus vietnamicus , new species, is superficially similar to A. quadridentatus , but the more developed first three anterolateral teeth serve to distinguish the latter species which has the first tooth very low. In addition, the chelae of A. quadridentatus are not as granular and inflated ( Figure 14A versus Figure 20A ) when compared with A. vietnamicus , new species. Most strikingly of course is the form of the G1, being truncated in A. quadridentatus but more elongate in A. vietnamicus , new species. This suggests that the form of the G1 may not be useful at the generic level.

Figures

Figure 14. Aniptumnus quadridentatus (De Man, 1895), „ (12×8 mm), NHM 2004.242. A, outer surface of right major chela; B, outer surface of left minor chela. Scale55.0 mm.

Figure 19. Aniptumnus vietnamicus new species, holotype, „ (7.9×5.7 mm), ZRC 1970.1.10.1. A, overall dorsal view; B, frontal view; C, ventral view. Scale510.0 mm.

Figure 20. Aniptumnus vietnamicus new species, holotype, „ (7.9×5.7 mm), ZRC 1970.1.10.1. A, outer surface of right major chela; B, outer surface of left minor chela. Scale55.0 mm.

Figure 21. Aniptumnus vietnamicus new species, holotype, „ (7.9×5.7 mm), ZRC 1970.1.10.1. A, left third maxilliped (setae denuded); B, anterior thoracic sternum (setae denuded); C, ventral view of right basis-ischium and merus of cheliped; D, right fourth ambulatory leg (setae denuded); E, subventral view of right third ambulatory merus (setae denuded); F, „ abdomen (setae denuded); G, H, left G1; I, J, distal part of left G1. Scales: A–F51.0 mm, G, H50.5 mm, I, J50.25 mm.