Enghoffosoma triangulare, 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 : 156-159

Enghoffosoma triangulare sp. nov.

( Figs 6–8 )

Material examined. Holotype male (IEBR-Myr 123H), Vietnam, Dong Nai Prov., Cat Tien National Park, forest, 24 September 2004, leg. Anh Duc Nguyen & S.I. Golovatch.

Paratypes: 1 female, 1 juv. (IEBR-Myr 123P), together with holotype.

Diagnosis. The species is easily recognized by the paraterga being well-developed; the gonopod femorite cylindrical and slender, but somewhat curved in the middle, without processes; the solenomere is slightly spiralled, as large as the femorite at base, then tapering towards tip; distal part with a small pointed tooth; process e small and triangular.

Name. “ triangulare ”, an adjective in neuter gender to emphasize the triangular process e of the gonopod postfemoral region.

Description. Body length about 32.8 mm (male), 26.7 mm (female); width of midbody pro- and metazonae 2.4 mm (male), 2.0 mm (female) and 3.0 mm (male), 2.9 mm (female), respectively. Body generally shining, yellowish brown; four anteriolateral and posterolateral areas on metaterga darker. Antennae, legs, sterna and paraterga yellow.

Clypeolabral region densely setose. Epicranial suture evident, with 2+2 setae on vertex. Antennae long and slender, nearly reaching segment 4 when stretched laterally. In length, antennomere 6>2=5>1–7 ( Figs 6 A–C).

Collum ( Fig. 6 B) surface shining and smooth, with two rows of 4+4 and 2+2 setae; paraterga poorlydeveloped, rounded, not extending behind rear margin.

In width, head<segment 2=3<4<2=5–16, thereafter body gradually tapering towards telson. Prozonae shining and smooth. Metaterga finely granulated, slightly wrinkled in posterolateral areas, with a row of 2+2 setae and traces of a row of 3+3 setae before and after transverse sulcus, respectively. Transverse sulcus present on segments 5–19, thin and deep, reaching to base of paraterga, striolate at bottom, especially on segments of rear half of body.

Sides below paraterga rugose, with several transverse wrinkles. Pleurosternal carinae well-developed, ridgeshaped; caudal corner spiniform and drawn behind posterior margin, present until segment 16, thereafter missing. Stricture between pro- and metazonae narrow, striolate at bottom. Axial line distinct, thin.

Paraterga ( Figs 6 D–E) well-developed, beak-like, drawn behind posterior margin. Caudolateral corner acute, even pointed in most of caudal segments. Calluses small on poreless paraterga, but larger on pore-bearing ones.

Epiproct ( Figs 6 F, H) long and broadly truncated, with 2 small terminal tubercles. Tip with four spinnerets. Hypoproct subtriangular, with two small, distolateral, setiferous knobs ( Figs 6 F, H).

Sterna densely setose; longitudinal groove vague, whereas transverse one distinct, without modifications except for a densely setose, bifid, trapeziform lamina between male coxae 4 ( Fig. 6 G).

Legs ( Figs 6 D–E) thin and slender, about 1.5 times as long as midbody height (male). Prefemora not swollen. Femora without modifications. Tarsal brushes present on male leg-pairs 1–9, thereafter gradually thinning out.

Gonopod ( Figs 7–8 ) relatively simple. Coxite large, stout; distoventral part sparsely setose. Prefemorite densely setose, separated laterally from femorite by a transverse sulcus. Femorite slender, cylindrical, but somewhat curved ventrad, with neither processes nor other modifications. Postfemoral region consisting only of a solenomere, clearly separated from femorite by a cingulum. Solenomere slightly spiralled, as large as femorite at base, thereafter tapering towards tip; distal part with a small pointed tooth; process e small, triangular. Seminal groove running distodorsad entirely mesally along femorite before entering onto a thick solenomere.

Remarks. The species is clearly distinguished from other known Enghoffosoma species by its gonopod conformation. It seems to be more similar to E. lanceolatum Likhitrakarn et al., 2014 by the well-developed paraterga and the small process e. E. lanceolatum differs from the new species in the gonopod showing an apicoventral shelf and a pointed, parabasal subventral process.

The species was found in the Cat Tien National Park, southern Vietnam, where the best forests in the region are still being conserved.

Figures

FIGURE 6. Enghoffosoma triangulare sp. nov. Holotype, anterior segments, lateral view (A), dorsal view (B), ventral view (C); midbody segments, dorsal view (D), lateral view (E); posterior segments, lateral view (F); sternum between coxae 4, ventral view (G); hypoproct and paraprocts, ventral view (H). Scale = 1 mm.

FIGURE 7. Enghoffosoma triangulare sp. nov. Holotype, right gonopod, lateral view (A); mesal view (B). Scale = 1 mm.

FIGURE 8. Enghoffosoma triangulare sp. nov. Holotype, right gonopod, lateroventral view (A); postfemoral region, lateroventral view (B).