Enghoffosoma retrorsum, Nguyen, Anh D. & Golovatch, Sergei I., 2016

Nguyen, Anh D. & Golovatch, Sergei I., 2016, The millipede genus Enghoffosoma Golovatch, 1993 recorded in Vietnam for the first time, with descriptions of three new species (Diplopoda, Polydesmida, Paradoxosomatidae), Zootaxa 4139 (2), pp. 151-166 : 159-161

Enghoffosoma retrorsum sp. nov.

( Figs 9–11 )

Material examined. Holotype male (IEBR-Myr 124H), Vietnam, Dong Nai Prov., Cat Tien National Park, forest, 16–24 May 2006, leg. Anh Duc Nguyen & S.I. Golovatch; Paratypes: 4 males, 3 females (IEBR-Myr 124P), same data as holotype.

Diagnosis. The species is recognized by the paraterga being moderately developed; the gonopod femorite slender, with an apical shelf b; the solenomere at base shows a retrorse process p and a process e; the latter is welldeveloped, somewhat lobe-shaped, spiralling mesad.

Name. “ retrorsum ”, an adjective in neuter gender to emphasize a retrorse process p at the base of the gonopod solenomere.

Description. Body length about 22.5–24.5 mm (male), 23.2–26.3 mm (female); width of midbody pro- and metazonae 1.8–1.9 mm (male), 2.2 mm (female) and 2.2–2.4 mm (male), 2.7–2.8 mm (female), respectively. Holotype length 26.5 mm; width of midbody pro- and metazonae 1.9 mm and 2.3 mm, respectively. Body generally monochrome, somewhat brownish yellow, but dorsum more or less darker.

Clypeolabral region sparsely setose. Epicranial suture thin and distinct. Antennae slender, nearly reaching segment 3 if stretched laterally. In length, antennomere 6>5=2>1–7 ( Figs 9 A–B).

Collum ( Fig. 9 A) surface shining, finely microgranulate, with a row of 1+1 setae near anterior margin. Paraterga poorly-developed, rounded.

In width, segment 4<3<head=collum=2=5=17, thereafter body gradually tapering towards telson. Pro- and metazonae finely microgranulate. Metaterga with traces of a row of 2+2 setae on front halves. Metatergal transverse sulcus thin, line-shaped, starting with segment 4, but completely developed on segments 5–19. Pleurosternal carinae well-developed, ridge-shaped on segments 2–7, thereafter missing. Stricture between pro- and metazonae narrow, neither beaded nor striolate. Axial line missing.

Paraterga ( Figs 9 A–C, D–E) modestly developed, small, keel-like. Caudolateral corner acute, drawn behind posterior margin, especially clearly so in caudalmost segments. Calluses strongly reduced, more obvious only on pore-bearing paraterga.

Epiproct ( Figs 9 F–H) broadly truncated, without terminal tubercles. Tip with four spinnerets. Hypoproct subtriangular, with two small, distolateral, setiferous knobs ( Figs 9 H–I).

Sterna modestly setose; longitudinal groove vague, whereas transverse one distinct, without modifications except for a rounded lamina between male coxae 4 ( Fig. 9 C).

Legs ( Figs 9 D–E) slender, about 1.5 (male) or 1.2 times (female) as long as body height. Prefemora not swollen. Femora without modifications. Tarsal brushes present, very thick on legs 1–9, gradually thinning out on legs 10–17, thereafter missing.

Gonopod ( Figs 10–11 ) relatively simple. Coxite long, cylindrical; distoventral part sparsely setose. Prefemorite densely setose, separated laterally from femorite by a subtransverse sulcus. Femorite long, slender and subcylindrical, somewhat curved in distal part, with an apical shelf b. Postfemoral region consisting only of a solenomere, clearly separated from femorite by a distinct cingulum. Solenomere large, suberect, strongly coiled distally, at base with a retrorse process p and a process e. The latter well-developed, more or less lobe-shaped, curved mesad. Seminal groove running distodorsad entirely mesally along femorite before entering onto a thick solenomere.

Remark. The species was found in the Cat Tien National Park, southern Vietnam, where the best forest in the region is being conserved.

Figures

FIGURE 9. Enghoffosoma retrorsum sp. nov. Holotype, anterior segments, dorsal view (A), lateral view (B); midbody segments, dorsal view (D), lateral view (E); posterior segments, dorsal view (F), lateral view (G), ventral view (H); sternum between coxae 4, ventral view (C); hypoproct and paraprocts, ventral view (I). Scale = 1 mm.

FIGURE 10. Enghoffosoma retrorsum sp. nov. Holotype, right gonopod, lateral view (A); mesal view (B). Scale = 1 mm.

FIGURE 11. Enghoffosoma retrorsum sp. nov. Holotype, right gonopod, mesal view (A); postfemoral region, mesal view (B).