Enghoffosoma digitatum, 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 : 162-165

Enghoffosoma digitatum sp. nov.

( Figs 12–14 )

Material examined. Holotype male (IEBR-Myr-107H), Vietnam, Dong Nai Prov., Cat Tien National Park, forest, 23–26 September 2004, leg. Anh Duc Nguyen. Paratypes: 3 males, 1 female (IEBR-Myr-107P), same data as holotype.

Diagnosis. The species is recognized by the paraterga being well developed; the gonopod postfemoral region consisting only of two processes: a thick, finger-shaped solenomere and a large, short, obscure, tuberculiform process e.

Name. “ digitatum ”, an adjective in neuter gender to emphasize the finger-shaped solenomere.

Description. Body length about 35.2–37.1 mm (male), 41 mm (female); width of midbody pro- and metazonae 2.9–3.0 mm (male), 3.7 mm (female) and 3.9–4.0 mm (male), 4.5 mm (female), respectively. Holotype length about 37.1 mm; width of pro- and metazonae ca. 3.0 and 4.0 mm, respectively. Body uniformly castaneous brown except for yellow paraterga and sterna.

Clypeolabral region densely setose. Epicranial suture thin, line-shaped, distinct. Antennae short, claviform, nearly reaching to the end of segment 3 if stretched laterally. In length, antennomere 2=3=4=5=6>7>1 ( Figs 12 A– B).

Collum nearly semi-circular; surface shining and smooth, with at least two rows of 3+3 and 3+3 setae. Paraterga broadly triangular, without lateral incisions.

In width, segment 3<4<head<collum=2=5–17, thereafter body tapering towards telson. Prozonae and sides below pataterga finely shagreened. Metazonae shining, with a row of 3+3 on fore halves. Metatergal transverse sulcus thin, line-shaped, starting with segment 4, but completely developed, reaching to base of paraterga on segments 5–19. Pleurosternal carinae well-developed, ridge-shaped, with a caudal acute denticle on segments 2– 10, reduced to a caudal acute denticle on segments 11–17, thereafter completely missing. Stricture between pro- and metazonae shallow, clearly striolate at bottom. Axial line thin and distinct.

Paraterga ( Figs 12 D–F) well developed, largely horizonal, only caudolateral corners somewhat upturned, but still lying below dorsum. Paraterga of segment 2 flabelliform, other paraterga subtriangular with a broadly rounded fore corner. Caudolateral corner acute, produced behind rear tergal margin into a small pointed tubercle in caudalmost segments ( Fig. 12 F). Calluses thin, but more obvious on pore-bearing paraterga, without lateral incisions.

Epiproct ( Figs 12 G–I) long, broadly truncated, without terminal tubercles. Tip not concave, with four spinnerets. Hypoproct broadly triangular, with two small, distolateral, setiferous knobs ( Figs 12 H–I).

Sterna densely setose; cross-impression distinct, with a small cone caudally near each coxa, rear cones being somewhat larger than fore ones. Male sternum 5 with a large, densely setose, trapeziform process between coxae 4 ( Fig. 12 C).

Legs ( Fig. 12 E) about 1.4–1.5 times as long as midbody height (male). Male prefemora swollen dorsally. Femora without modifications. Tarsal brushes present until male leg 10, thereafter gradually thinning out.

Gonopod ( Figs 13–14 ) relatively simple. Coxite large and stout, about half as long as femorite; distoventral part sparsely setose. Prefemorite densely setose, separated laterally from femorite by a subtransverse sulcus. Femorite suberect, subcylindrical, long, weakly constricted at 2/3 of its extent, with neither processes nor other modifications. Postfemoral region consisting only of a solenomere and a process e, clearly separated from femorite by a cingulum. Solenomere very thick, oblique, finger-shaped, pointed at tip. Process e large, obtuse, tuberculiform, slightly shorter than solenomere, somewhat curved ventrad. Seminal groove running distodorsad entirely mesally along femorite before entering onto a thick solenomere.

Remarks. The new species is fairly similar to E. bispinum Likhitrakarn, Golovatch & Panha, 2014 , from Rayong Province, Thailand, in the gonopod postfemoral region consisting only of a solenomere and a process e. However, E. bispinum differs in the gonopod femorite being slightly curved, the solenomere with a small process terminating the seminal groove in the distal part, and process e being pointed, erect, slightly shorter than the solenomere.

Figures

FIGURE 12. Enghoffosoma digitatum sp. nov. Holotype, anterior segments, dorsal view (A), ventral 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 13. Enghoffosoma digitatum sp. nov. Holotype, right gonopod, mesal view (A); lateral view (B). Scale = 1 mm.

FIGURE 14. Enghoffosoma digitatum sp. nov. Holotype, right gonopod, mesal view (A); postfemoral region, mesal view (B).