Hylomus yuani, Liu, Weixin & Wynne, J. Judson, 2019

Liu, Weixin & Wynne, J. Judson, 2019, Cave millipede diversity with the description of six new species from Guangxi, China, Subterranean Biology 30, pp. 57-94 : 69

Hylomus yuani sp. nov. Figs 3C , 9 , 10 , 11 , 12

Material examined.

Holotype male (SCAU), China, Guangxi Zhuang Autonomous Region, Lingchuan County, Liangfeng Cave [25°12'34.86"N, 110°31'56.8"E], 184 m el., deep zone, direct intuitive search, 18 November 2016, J.J. Wynne leg. Paratypes, 1 male, 3 females (SCAU), same data as holotype.

Etymology.

This species is named for Dr. Yuan Daoxian (袁道先), a preeminent and globally recognized Chinese hydrologist. He has made numerous significant contributions in advancing both the science and management of karst and karst waters in southern China since the 1960s.

Diagnosis.

Adult males of H. yuani sp. nov. are distinct from other Hylomus species based on the following combination of characters: (1) paraterga long and spiniform only on collum and rings 2-6, short and coniform thereafter ( Figs 9 , 10A, B ); (2) collum with 8+8 frontal, 3+3 in the middle, 3+3 caudal, setigerous spinules; (3) ♂ femur 6 strongly inflated in distal 1/4 ( Fig. 10D ); (4) gonopod with a flagelliform solenomere and a strongly condensed solenophore ( Figs 9 - 12 ). This new species is similar to H. lui (a troglobiont from a cave in Guilin), but is distinguished by (1) paraterga long and spiniform on collum and rings 2-6 ( Fig. 9 ) vs. on collum and rings 2-5 in H. lui ; (2) collum and following metaterga with three transverse rows of spinules ( Fig. 10 A–B ) vs. two transverse rows of spinules in H. lui .

Description.

Based on type specimens. Lengths of body ca 27-28 (♂), 30-35 mm (♀); width of mid-body pro- and metazonae 1.5-1.6 and 2.0 (♂), 2.0-2.2 and 2.5-2.6 mm (♀). Coloration: light brownish to nearly pallid ( Figs 3C , 9 - 10 ). Antennomere 7 dark brown. Body: with 20 rings. In width, head <ring 2 <collum <4-5 <3 = 6-7 <8-9 <10-13; thereafter body gradually tapered posteriorly towards telson. Head: densely setose, but more sparsely on vertex, epicranial suture conspicuous ( Fig. 10A ). Antennae long and slender, reaching past ring 8 (♂) or 7 (♀) when extended posteriorly. Exoskeleton: Collum with 8+8 evident setigerous spinules arranged in a row at front margin, behind it with 3+3 in the middle and 3+3 similarly spinules at posterior margin. Metaterga 2-4 each with 5+5, 3+3 and 5+5(6) similarly setigerous spinules arranged in three transverse rows ( Fig. 9A ). Following metaterga with same sculpture, but 7 –9+7– 9 setigerous spinules at posterior margin, 2-4 spinules of them extended to the lateral side ( Figs 9C , 10B ). Paraterga clearly spiniform, but well-developed only in paraterga 1-6, directed more dorsad than laterad ( Fig. 9A ). Following paraterga increasingly stout and short, paraterga 7-14 directed dorsolaterad, thereafter directed clearly caudad ( Figs 9C , 10 A–B ). Tegument shining, prozonae delicately microalveolate, metaterga and surface below paraterga finely microgranulate. Constriction between pro- and metazonae broad and shallow ( Fig. 10 A–B ). Pore formula normal; transverse sulcus usually very vague, but traceable in rings 5-19 ( Fig. 10A ). Ozopores inconspicuous, located near the base on lateral side of pore-bearing paraterga ( Fig. 10B ). Pleurosternal carinae evident only on rings 2 and 3 in both sexes, absent thereafter. Epiproct simple, lateral pre-apical papillae distinct ( Fig. 9C ). Hypoproct subtrapeziform, caudal margin emarginate, setigerous cones at caudal edge large, widely separated ( Fig. 9D ). Sterna sparsely setose, cross-shaped impressions weak. A paramedian pair of short, rounded, independent tubercles between ♂ coxae 4 ( Figs 9B , 10C ). Legs long and slender, ca 5.0 (♂) or 3.5 (♀) times as long as mid-body ring height. ♂ femur 6 strongly inflated ventrally in distal 1/4 ( Fig. 10D ). Gonopods: ( Figs 11 , 12 ) Coxite short, subcylindrical, densely setose distodorsally, about 1/3 as long as telopodite. Prefemur densely setose and about half as long as acropodite. Femorite elongate, slightly curved, with seminal groove running entirely on mesal face. Solenophore (sph) strongly condensed; solenomere (sl) flagelliform, evidently separated at base from solenophore.

Habitat.

This species was collected within the estimated cave deep zone, approximately 20 m from the cave entrance. Cave sediment was compact mud and the passageway was swaddled by a slightly visible fog. This species and cave crickets (family Rhaphidophoridae ) were among the most abundant species within this portion of cave deep zone.

Notes.

Based on the slender elongate antennae and legs, a depigmented cuticle, the species is considered a troglobiont.

Figures

Figure 3. A Hyleoglomeris rukouqu sp. nov. from Shangshuiyan Cave B Hyleoglomeris xuxiakei sp. nov. from Guanshan No. 4 Cave C Hylomus yuani sp. nov. from Liangfeng Cave D Eutrichodesmus jianjia sp. nov. from Guanshan No. 4 Cave.

Figure 9. Hylomus yuani sp. nov., ♂ paratype. A Anterior part of body, dorsal view B anterior part of body, ventral view C posterior part of body, dorsal view D posterior part of body, ventral view.

Figure 10. Hylomus yuani sp. nov., ♂ paratype. A Mid-body rings, dorsal view B mid-body rings, lateral views C sternite V, ventral view D femora 6 and 7, subventral view.

Figure 11. Hylomus yuani sp. nov., ♂ paratype. A Right gonopod, lateral view B right gonopod, mesal views.

Figure 12. Hylomus yuani sp. nov., ♂ paratype. A Right gonopod, lateral view B right gonopod, mesal views. Designations: sl = solenomere; sph = splenophore.