Xystodesmus kumeensis Korsós & Nakamura, 2025, sp. nov.
Creators: name: Korsós, Zoltán
name: Nakamura, Yasuyuki
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Diplopoda
Polydesmida
Xystodesmidae
Xystodesmus
Xystodesmus kumeensis

description: Xystodesmus kumeensis sp. nov.
Figs 5 A – F, 16 C
Type material.
Holotype: • male, Japan, Central Ryukyus, Okinawa Pref., Okinawa Group, Kume-jima Isl., Kanegusuku – Self Defense Force base, 2.2 km from pref. road, 90 m a. s. l., 23 February 1992, leg. T. Tanabe (NSMT -My 539). Paratypes: • 4 females (NSMT -My 540) same locality and date; • 1 male, 1 female, Japan, Central Ryukyus, Okinawa Pref., Okinawa Group, Kume-jima Isl., Uegusuku shrine, 26°22'35"N, 126°46'20"E, 235 m a. s. l., from roots of Ficus tree, 7 November 2011, leg. A. and Z. Korsós (RUMF -ZD-00946 [male] and - 00947 [female]); • 2 males, Japan, Central Ryukyus, Okinawa Pref., Okinawa Group, Kume-jima Isl., Daruma-yama forest road, 26°22'07"N, 126°45'50"E, 204 m a. s. l., 9 November 2011, leg. A. and Z. Korsós (HNHM diplo-04543).
Other non-type material.
18 juveniles, same locality and date as holotype (NSMT -My 541).
Diagnosis.
Medium-sized Xystodesmus, male with essentially simple, two-branched gonopod, and a small, isolated coxal apophysis. Most similar to X. rebekae sp. nov., X. gracilipes, and X. nikkoensis, but differs from them by the presence of a coxal apophysis and by the configuration of the prefemoral and tibiotarsal processes. Prefemoral process is strongly twisted, longer than acropodite, at approximately midpoint with a small tooth, whereas in all the three others it is straight, slender, and subequal to acropodite, without tooth. In X. nikkoensis, acropodite has ventrally a small triangular process which is missing in X. kumeensis sp. nov.
Description.
Length 30–32 mm, midbody width with paraterga 5.5–6.2 mm, midbody metatergal length 1.4–1.8 mm, collum width 4.2–4.9 mm, median collum length 1.9–2.4 mm. Body sides between segments 5–14 subparallel.
Head smooth, epicranial suture distinct. Antennal articles slightly clavate, first article sub-globose, articles 2–6 subequal in length, 2 and 3 are most clavate, 4–6 almost straight, article 7 small, as long as wide, slightly tapering to its tip.
Pro- and metaterga completely smooth, transverse depression in metaterga hardly noticeable. Collum in dorsal view almost oval, edges rounded, with only very weak ridges, lateral corners directed ventrad, length along median line ~ 2 × as long as metatergum 2. Anterior edge of paranota 2–4 rounded, posterior edge rounded, lacking projection. Posteriolateral triangular projection starts on metaterga 5, from 6 onwards increasingly pointed, sublateral excavations on caudal margin of midbody segments strong, semicircular. Lateral sides of paranota arched, outline of segments clearly delimited. Pore formula normal, pores in lateral central position on narrow paranota.
Segments 15–19 gradually tapering, caudal corners becoming more pointed. Epiproct protruding, in lateral view slightly curved, thick, with 2 + 2 large setae on each lateral side on tubercles, projection with 2 + 2 setae apically (i. e., 6 pairs of setae altogether); paraprocts smooth, with two pair of setae on strong median ridges; hypoproct semicircular with two setae on small tubercles.
Bases of midbody leg pairs well separated (by 1.2 mm in male, 1.6–1.8 mm in females), sterna smooth and wide, pro- and metasterna well separated. Coxa short, just a little bit longer than wide; prefemur ~ 1.2 × longer, on postgonopodal legs with well-developed ventral spine; femur 2 × as long as coxa, incrassate; postfemur short again like coxa, tibia, and tarsus subequal in length, both ~ ½ as long as femur; claws normal on all legs.
Colour of living specimens pale brown, almost yellowish, paranotal spots hardly visible (Fig. 16 C). Preserved specimens show faded pattern typical for Xystodesmus: metaterga slightly darker, proterga paler, clypeus light brownish, underside of head, antennae, legs, epiproct, and whole ventral side yellowish white.
Male sexual characters. Second leg pair with tubulous coxal processes, sterna of segments 4–6 and further legs without any modifications. Gonopods (Fig. 5 A – C): Coxa stout, ~ 1.5 × longer than wide, coxal apophysis (ca) present in form of a small bump emerging from a circular field, next to a short, thick apophyseal macroseta (ms). Prefemur stout, subparallel-sided, densely setose only on ventral side; prefemoral process (pfp) slender, longer than acropodite, strongly curved into a sharp, pointed tip, at approximately midpoint with a widely based, triangular side tooth (Fig. 5 B, t); acropodite (a) slim, more slender than prefemoral process, only ~ 2 / 3 of its length, almost straight, gradually tapering towards tip, slightly broadening before pointed tip into a leaf-like lamella (Fig. 5 B, l). Prostatic groove runs straight on the mesal side of acropodite.
Female sexual characters. Coxae of 2 nd leg pair with a pair of small, pointed, setose projections (Fig. 5 D). Cyphopods (Fig. 5 E, F) situated in deep, joint aperture behind leg pair 2, loosely encapsulated in vulval sacs, well separated from each other. Receptacula (r) both on anterior and posterior side, densely setose; anterior receptaculum low, broad, posterior one high, slender, higher than bursal valves; operculum (op) small, rounded, situated laterad, in anterior view hardly visible; bursal valves (v) equal shaped, broad, rectangular, with short setae, without pointed apices.
Remarks.
The species was treated as an uncategorised population under Xystodesmus in Tanabe and Shinohara (1996: Cluster I, figs 7, 11 Q, 16 H, 17 R). The individuals were found on Kume-jima Island in mixed Pinus luchuensis and broad-leaved evergreen forest.
Etymology.
Named after the collecting locality, Kume-jima Island, west of Okinawa-jima Isl., where the species is probably endemic to. Adjective, masculine.
description: Published as part of Korsós, Zoltán & Nakamura, Yasuyuki, 2025, Review of the millipede genus Xystodesmus (Diplopoda, Polydesmida), with seven new species from the southwestern part of Japan, pp. 191-232 in ZooKeys 1231 on pages 191-232, DOI: 10.3897/zookeys.1231.141443