Hylomus solenophorus, Nguyen & Nguyen & Eguchi, 2021

Nguyen, Anh D., Nguyen, Dai Dac & Eguchi, Katsuyuki, 2021, Mountainous millipedes in Vietnam. I. Two new species of the family Paradoxosomatidae from Mount Fansipan (Diplopoda, Polydesmida), ZooKeys 1032, pp. 1-15 : 1

publication ID	https://dx.doi.org/10.3897/zookeys.1032.64917
publication LSID	lsid:zoobank.org:pub:E45C61A8-6565-4AB5-B5FC-AD907A9B4738
persistent identifier	https://treatment.plazi.org/id/2BAC98BA-8221-4C8B-B1B5-63ACD3534CE9
taxon LSID	lsid:zoobank.org:act:2BAC98BA-8221-4C8B-B1B5-63ACD3534CE9
treatment provided by	ZooKeys by Pensoft
scientific name	Hylomus solenophorus
status	sp. nov.

Treatment

Hylomus solenophorus sp. nov. Figs 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10

Material examined.

Holotype. male (IEBR-Myr 712), Vietnam, Lao Cai Province, Hoang Lien National Park , natural forest, 22.32250°N, - 103.77081°E, 2478 m a.s.l., 7 July 2018, coll. Nguyen Dac-Dai. GoogleMaps Paratype. 1 male, 1 female (IEBR-Myr 714), Lao Cai Province, Hoang Lien National Park , natural forest, 22.32129°N, - 103.77094°E, 2547 m a.s.l., 7 July 2018, coll. Nguyen Dac-Dai. GoogleMaps

Diagnosis.

The species differs from its congeners by having wing paraterga, two rows of 2+2 and 2+2 knobs on the metaterga, and a well-developed, broad gonopod solenophore with an additional distal process.

Description.

Holotype body length about 16.0 mm, width of pro- and metazona 1.2 mm and 2.0 mm, respectively.

Coloration (Figs 6 View Figure 6 , 7 View Figure 7 ): whole body blackish brown or black, except labrum, sterna and legs yellowish brown. Projected caudal corners of paraterga yellowish brown.

Head (Fig. 6C, D View Figure 6 ) slightly smaller than body segments, but somewhat larger than collum. Epicranial suture clearly distinct; frons with 2+2 setae along epicranial suture. Clypeolabral region moderately setose. Antenna extremely long, reaching segment 5 if stretched laterally; antennomere 3=4=5>2>6>1>7; tip with four sensory cones.

Collum (Fig. 6A View Figure 6 ) slightly smaller than segment 2, semicircular; surface not smooth, with 3 rows of setiferous knobs: 3+3 anterior, 2+2 intermediate and 1+1 posterior; transverse sulcus present, located near a row of 1+1 posterior knobs. Paratergum broadly triangular, well developed, with a lateral incision (Fig. 6A View Figure 6 ).

Body segment 3<4<2=5-17, thereafter gradually tapering toward telson (Figs 6A, B View Figure 6 , 7A-C View Figure 7 ). Prozonae smooth, shagreened while metazonae densely covered with microgranulation. Transverse metatergal sulci shallow, broad, present on all segment. Metaterga 2-4 with two rows of setiferous knobs: 2+2 and 2+2 in front of and behind transverse sulcus, respectively; other metaterga with two rows of 2+2 and 3+3 setiferous knobs. Axial line distinct, thin. Waist between pro- and metazonae indistinct, shallow, and broad. Pleurosternal carinae absent.

Paraterga (Figs 6A View Figure 6 , 7A-C View Figure 7 )) wing-shaped, with pointed, projected caudal corners, lying horizonally, but reduced as broad-base spine with two lateral incisions on segments 7-18.

Epiproct long, broadly truncated, flattened dorsoventrally; tip with four spinnerets (Fig. 7D View Figure 7 ). Hypoproct trapeziform, with two distolateral, separated setiferous knobs (Fig. 7D View Figure 7 ).

Sterna sparsely setose, with distinct cross-impressions, without modifications except for an anterioventrally directed, large, strongly bi-lobuled process between coxae 4 (Fig. 8A, B View Figure 8 ).

Legs slender, long about 1.5-1.7 times as long as midbody height. Prefemora not swollen. Femora without modifications. Tarsal brushes absent.

Gonopods simple (Figs 8C, D View Figure 8 , 9 View Figure 9 , 10 View Figure 10 ). Coxite cylindrical, distoventral part sparsely setose. Prefemorite densely setose, set off from femorite by an oblique sulcus laterally. Femorite slightly curved mesad, somewhat enlarged distally, without modifications and processes. Demarcation between femorite and postfemoral region absent. Postfemoral region consisting of solenophore and solenomere. Femorite and solenophore subequal in length. Solenophore simple, broad, slightly spiral and somewhat curved down. Tip of gonopod broadly round, with an additional distoapical process. Seminal groove running entirely on mesal side of femorite, then entering the flagelliform solenomere sheathed by solenophore.

DNA characters.

Fragments of COI and 16S rRNA were uploaded to GenBank with accession numbers: MW647899 and MW648328, respectively. The new species has a close COI identity with Hylomus cervarius (MG669370) and Hylomus enghoffi (MG669369) of 85.1% and 83.45%, respectively. It also shares 79.57% and 78.72% of its 16S rRNA gene sequence with Hylomus cervarius (MG564329) and Hylomus enghoffi (MG564330), respectively.

Etymology.

An epithet " Hylomus solenophorus " is used to emphasize the well-developed, broad solenophore carrying a triangular distoapical process.

Remarks.

The genus Hylomus Cook & Loomis, 1924 used to be a synonym of the genus Desmoxytes Chamberlin, 1923 ( Golovatch and Enghoff 1994), but it was recently re-evaluated by Srisonchai et al. (2018) and currently comprises 39 species ( Sierwald and Spelda 2021). The new species differs distinctly from the majority of known Hylomus species (except for H. spectabilis ) in having wing-shaped paraterga (vs. antler-like or spiniform paraterga). As already stated, Hylomus solenophorus sp. nov. is closely similar to H. spectabilis (Attems, 1937) from central Vietnam by having wing-shaped paraterga and the same gonopod conformation. On the other hand, the newly described species differs clearly from H. spectabilis by being smaller in size (length: 16 mm vs. 30 mm; width of metazona: 2.0 mm vs. 6.1 mm) and having darker body coloration (darkish brown or black vs. brown). Furthermore, leg femora of the new species possess no visible modifications, metaterga contain two rows of 2 + 2 and 3 + 3 setiferous knobs and the gonopod has no spine z, but possesses a triangular distoapical process, instead. By comparison, the 7th femur of the H. spectabilis male has a ventral hump, metaterga are characterised by two transversal rows of 2 + 2 well-developed spines and 1 + 1 smaller spines and the gonopod is characterised by well-developed spine z, but no process k.