Riukiaria spina, Chen & Zheng & Jiang, 2023

Chen, Hui-Ming, Zheng, Chang-Bin & Jiang, Xuan-Kong, 2023, The millipedes (Diplopoda) in Yintiaoling National Natural Reserve, Southwest China, Zootaxa 5257 (1), pp. 49-81 : 77-80

Riukiaria spina sp. nov.

Figs 35–37

Type materials. Holotype male: China, Chongqing, Wuxi County, Yintiaoling National Nature Reserve, Linkouzi , 31°28’19.47” N, 109°52’58.34” E, alt. 1680 m, 17 August 2022, X.K. Jiang & H.M. Chen leg. Paratypes: 2 males and 1 female, same data as holotype .

Diagnosis. This species is very similar to R. davidiani Golovatch, 2014 from Sichuan in the slender and bent prefemoral process and solenomere of the gonopods, but differs from the latter by the prefemoral process of the gonopods only slightly bending mesially ( Figs 36A–C , 37A–C ) not forming semicircle as in R. davidiani .

Etymology. The species name is derived from the shape of the prefemoral process of the gonopods, meaning ‘spine’, noun.

Description. Length ca. 48–52 mm, midbody paranotal width 9.7–10.6 mm, metatergal length 4.1–4.8 mm, collum width 8.3–8.5 mm, length 3.3–3.6 mm. Body uniformly light yellow ( Fig. 35A ). Fluorescence in UV light strong ( Fig. 35B ).

Head smooth, epicranial suture distinct, several setae scattered above clypeus, with 2 dense rows at its margin and on labrum. Antennae slender. Antennomeres 1 and 7 short and small, slightly longer than wide. Antennomeres 2–6 clavate. Lengths of antennomeres: 6>5≈4≈3≈2>1>7. Gnathochilarium densely setose. Collum convex, smooth, shiny, without marginal ridge, tapering laterally. Pro- and metaterga smooth without any traces of tubercles or punctuation, not even wrinkles ( Fig. 35A ). Posteriolateral edge of paranota strongly pointed caudad. Pore formula normal, pores on paranota 5,7,9,10,12,13,15,16,17, and 18, in median excavation of paranota (in lateral view). Epiproct in dorsal view subtriangular, in lateral view protruding over paraprocts, parallel-sided, slightly curved ventrad, with 7+7 setae, 3+3 of them sitting on knobs. Paraprocts strongly marginate with 2+2 setae, hypoproct with 1+1 setae on knobs. Midbody legs well separated, sterna wide and smooth. Postgonopodal legs ( Fig. 36E ) with moderately developed ventral spine on prefemur, increasingly stronger towards body end. Femur as long as tarsus. Postfemur stout, about half-length of femur. Tibia straight, both subequal in length of postfemur. Tarsus slender. Claw curved.

Male 2nd leg pair coxa with strong median projections about half as long as length of coxa, densely setose, without membraneous tubules apically ( Fig. 36D ). Male gonopodal aperture on segment 7 wide, elliptical, about twice as wide as long, gonopods in situ usually deeply embedded, with acropodites crossing each other.

Coxa of gonopod ( Figs 36A–C , 37 ) stout, approximately as long as wide, glabrous, without proximal apophysis. Cannula normal, situated on mesal side ( Figs 36B, C ; 37B, C ). Telopodite consists of two slender and simple processes, prefemoral process and acropodite (solenomere), typical for Riukiaria . Prefemur densely covered with long hairs. Base of prefemoral process developed, originated from the base of prefemur. Prefemoral process extremely slender, spine-like bending mesially, as long as acropodite, with no setae, hairs, or processes. Acropodite long, scythe-shaped with a sharp tip, arched proximally towards prefemoral process. Prostatic groove running along mesal side, and ending on the pointed tip ( Fig. 37B ).

Distribution. Known only from the type locality.

Remarks. Riukiaria contains 36 species distributed in China and Japan ( Marek et al. 2014). In China, thirteen species have been reported from Shaanxi (1 species), Sichuan (2 species), Zhejiang (2 species), Fujian (1 species) and Taiwan (7 species). Riukiaria spina sp. nov. is the first species of Riukiaria reported from Chongqing.

Figures

FIGURE 35. Live specimen of Riukiaria spina sp. nov. A. In visible light; B. In UV-light.

FIGURE 36. Riukiaria spina sp. nov., holotype. A. Left gonopod, lateral view; B. Left gonopod, ventral view; C. Left gonopod, mesal view; D. Sternum, coxa, and prefemur of 2nd legpair, posterior view; E. Midbody leg, anterior view. Scale bars: A−C = 0.75 mm; D = 0.5 mm; E = 1 mm.

FIGURE 37. Riukiaria spina sp. nov., holotype. A. Left gonopod, lateral view; B. Left gonopod, ventral view; C. Left gonopod, mesal view; D. Sternum, coxa, and prefemur of 2nd legpair, posterior view; E. Midbody leg, anterior view. Scale bars: A−C = 0.75 mm; D = 0.5 mm; E = 1 mm. Abbreviations: c, coxa; pfp, prefemoral process; sl, solenomere.