Xystodesmus kumamotoensis, Korsós & Nakamura, 2025

Xystodesmus kumamotoensis sp. nov.

Figs 3 A – D View Figure 3 , 4 A – C View Figure 4

Type material.

Holotype: • male, Japan, Kyushu, Kumamoto Pref., Yatsushiro City, Toyo Town, Kawamata, Kaerizaka, along prefectural road No. 25 , 32°30'31.4"N, 130°45'42.5"E, 230 m a. s. l., 17 November 2008, leg. M. Nakano ( NSMT -My 537 ) GoogleMaps . Paratypes: • 1 male, 2 females, same locality and date ( NSMT -My 538 ) GoogleMaps ; • 1 male, Japan, Kyushu, Kumamoto Pref., Yatsushiro City, Toyo Town, Kawamata, Tsurukoba, along prefectural road No. 25 , 32°28'45.9"N, 130°45'11.2"E, Cryptomeria japonica forest, 700 m a. s. l., 18 September 2009, leg. T. Iihoshi ( RUMF -ZD-00940 ) GoogleMaps ; • 2 males, Japan, Kyushu, Oita Pref., Hita City, Kamitsue Town, Kawahara , 33°06'58.8"N, 130°57'50.9"E, along National Road No. 387, Cryptomeria japonica forest, 14 November 2008, leg. T. Menda ( HNHM diplo-04542 , NHMD 1184732 ) GoogleMaps .

Diagnosis.

Relatively small Xystodesmus with colour pattern faded from preservation in ethanol but still typical for the genus. (Unfortunately, this is the only species of which we did not have live colour photo.) Gonopod completely lacks coxal apophysis as in the most similar species X. shirozui (Takakuwa, 1942) , but differs from it by the widely bifurcated acropodite and the laminate, tongue-like prefemoral process.

Description.

Length 26–27 mm, midbody width with paraterga 4.8–5.0 mm, midbody metatergal length 1.2–1.3 mm, collum width 3.8–3.9 mm, median collum length 1.9 mm. Body sides between segments 5–16 subparallel.

Head smooth, with two frontal setae, epicranial suture distinct. Antennal articles straight, slender, first article short, 1.5 × longer than wide, articles 2–6 subequal in length, 7 small, with length equal to width.

Proterga completely smooth, metaterga weakly wrinkled, each with a shallow transverse depression in the middle. Collum subtrapezoid-shape, arched, 1.5 × longer than metatergum 2, lateral edges directed posterioventrad, anteriolateral margin with well visible ridge. Posterior edge of paranota 2–5 rounded, triangular projection only starts from segment 6 onwards, posterior margin of each metaterga straight, sublateral excavations hardly detectable. Lateral sides of paranota straight, almost giving a parallel straight outline to the body. Pore formula normal, pores in lateral position on narrow paranota.

Segments 17–19 gradually tapering, posteriolateral corners becoming more pointed. Epiproct protruding, in lateral view slightly curved, with two pairs of setae on small side tubercles, and with two setae apically; paraprocts smooth, with two pair of setae on obvious median ridges; hypoproct subtriangular.

Bases of midbody leg pairs clearly separated (by 1.1 mm), sterna smooth and wide, pro- and metasterna also clearly separated. Postgonopodal prefemora with well-developed ventral spine, increasingly larger from midbody legs onwards, femur 1.5 × longer than prefemur, slightly bent proximad, postfemur short and curved, tibia slender, tarsus 1.5 × longer than tibia, claws normal on all legs.

Colour of living specimens unknown. Preserved specimens show faded pattern typical for Xystodesmus : metaterga slightly darker, proterga paler, paranota with pale orangish / yellowish spot. Clypeus light brownish, underside of head, antennae, legs, epiproct, and whole ventral side light pale white.

Male sexual characters. Second leg pair with tubulous coxal processes (Fig. 3 D View Figure 3 ), densely setose. Sterna of segments 4 and 5 (Fig. 4 A, B View Figure 4 ) with a pair of protruding processes, on segment 4 longer, pointed, without setae, on segment 5 lower, widely separated from each other, without setae. Other legs and sterna without modifications. Gonopods (Fig. 3 A – C View Figure 3 ): Coxa short and thick, almost as wide as long, no trace of apophyseal process, only a strong single seta (ms) on the anteriomesal side. Prefemur stout, nearly straight, densely setose, prefemoral process (pfp) broad and flat, lamellate, ~ 2 × as song as wide, subrectangular from ventral view, distal margin slightly serrated (Fig. 3 B View Figure 3 ). Acropodite (a) delimitated from prefemur by a weak constriction, its length only a little longer than prefemoral process, and soon divided into two branches subequal in length, directed anteriorly and gradually tapering to their pointed tips. Prostatic groove runs to the tip of the branch situated laterad, which is also provided with a small tooth (Fig. 3 B View Figure 3 , t) on it lateral side, best visible in situ from direct ventral view.

Female sexual characters. Cyphopods (Fig. 4 C View Figure 4 ) situated in deep, joint excavation behind leg pair 2, loosely encapsulated in vulval sacs, well separated from each other. Receptacles (r) both on anterior and posterior side, densely setose; operculum (op) situated laterally, small, rounded, with numerous short setae; valves (v) hairless, mesally with conspicuous pointed apices, closely parallel to each other.

Remarks.

In the type locality and Toyo Town, 700 m a. s. l., Riukiaria semicircularis semicircularis (Takakuwa, 1941) and R. cornuta ( Haga, 1968) were also found. In Hita City, R. semicircularis semicircularis and Parafontaria tonominea (Attems, 1899) were also found together with the new species.

Etymology.

Named after the locality, Kumamoto Pref., Kyushu, Japan. Adjective, masculine.