Sinonychus luodianensis Jiang & Chen, 2025

Jiang, Ri-Xin & Chen, Xiang-Sheng, 2025, Two new species of the genus Sinonychus (Coleoptera, Elmidae) from Guizhou, China, ZooKeys 1223, pp. 57-67 : 57-67

Sinonychus luodianensis Jiang & Chen sp. nov.

Figs 1 B, D , 3 A – F , 4 H – N (罗甸华溪泥甲 )

Type material.

41 exs: 11 ♂♂, 10 ♀♀, 20 exs., sex undetermined. Holotype: • CHINA: ♂, labeled “ China: Guizhou, Qiannan Buyi and Miao Autonomous Prefecture (黔南布依族苗族自治州), Luodian County (罗甸县), Luokun Town (罗悃镇), Xiangshui Village (响水村), 25°19'43"N 106°38'28"E, H: 666.10 ± 6.40 m, 09. XI. 2022, Jiang Ri-Xin leg. ” ( GUGC) . Paratypes: • 10 ♂♂, 10 ♀♀, 20 exs., sex undetermined, with same label data as the holotype ( GUGC) .

Diagnosis.

Body long-oval, mostly black; pronotum (except basal part), antennae, base of tibia and tarsi (including claws) light brown. Plastron setae scaly. Elytral intervals 5, 6 and 7 with granulate carinae. Aedeagus with apex of median lobe rounded; median lobe with two pairs of long, elongate sclerotizations located at basal 1 / 2; a very thin and long sclerotization extends from middle of median lobe to well beyond the apex, where it is curved.

Description.

Body long-oval (Fig. 1 B ); black with pronotum (except basal part), antennae, base of tibia and tarsi (including claws) light brown. Plastron setae confined to following areas: head (both dorsal and ventral surfaces, including disc of clypeus); pronotum (lateral areas); elytra (lateral areas, including epipleura); prosternum, mesoventrite, metaventrite and abdomen (lateral areas); and femora.

Head (Fig. 3 A ), wider than long, surface covered with plastron setae and sparse, long setae and granules. Clypeus with disc covered with plastron setae; anterior and lateral areas without plastron setae, covered with sparse, long setae. Labrum transverse, narrower than clypeus, lateral margins with long bristles. Antenna (Fig. 1 D ) 7 - segmented with apical antennomere clubbed.

Pronotum (Fig. 3 B ) slightly wider than long, widest at basal 2 / 5, gradually narrowed from basal 2 / 5 to apex. Surface finely punctate; covered with sparse, long setae and with plastron setae laterally. Median longitudinal sulcus distinct and long, extending from base nearly to anterior 1 / 4, with a pair of small round fovea near base. Sublateral grooves straight, short, less than 1 / 3 length of pronotum. Anterior margin distinctly curved, anterior angles not produced. Lateral margins gradually curved. Basal margin trisinuate, emarginate anterior to scutellum, posterior angles nearly orthogonal. Prosternal process (Fig. 3 C ) very wide, with apex broadly rounded; surface distinctly microreticulate, glabrous.

Scutellum (Fig. 3 B ) cordate, longer than wide, widest at basal 1 / 4; surface microreticulate and glabrous. Anterior margin strongly curved, lateral margins weakly curved, apex acutangular.

Elytra (Fig. 3 F ) about 1.5 times as long as wide, widest near in median 1 / 3. Strial punctures large in basal 2 / 3 of elytra, separated by about twice a diameter; much smaller and more widely separated in other parts of elytra. Elytral intervals 5, 6, 7 with granulate carinae extending from base of elytra nearly to apex. Interval 5 to lateral margins covered with plastron setae. Hing wings reduced.

Metaventrite (Fig. 3 D ) with disc distinctly microreticulate and covered with sparse, long setae; lateral areas with plastron setae. Median sulcus shallow and indistinct, less than half the length of metaventrite.

Admedian carinae of abdominal ventrite 1 indistinct, straight, extending from base to near apex. Median areas of ventrites 1–4 (Fig. 3 E ) and anteromedial area of ventrite 5 microreticulate, covered with sparse, long setae; remaining surface of ventrites 1–5 covered with plastron setae and mixed with sparse, long setae.

Legs simple, surface granulate (except tarsi). Surface of femora surface covered with plastron setae; inner side of tibia with cleaning fringes; tarsi slightly shorter than tibiae; tarsal claws simple.

Aedeagus (Fig. 4 H – K ) slender and elongate. Median lobe symmetrical, widest at base, weakly narrowed from base to apex; apex rounded; with two pairs of long, elongate sclerotizations located at basal 1 / 2; a very thin, very long sclerotization extends from middle of median lobe to well beyond the apex, where it is curved. Sternite IX (Fig. 4 L ) with apical margin weakly emarginate, without setae, median strut curved at middle with base curved.

Measurements: CL: 1.03–1.11 mm; PL: 0.33–0.35 mm, PW: 0.42–0.44 mm; EL: 0.70–0.78 mm, EW: 0.50–0.54 mm.

Female externally similar to the male, averaging larger. Ovipositor as in Fig. 4 M, N : valvifer about twice as long as coxite, distinctly expanded at base; coxite apex strongly expanded, roundly broadened at outer margin; stylus short, weakly curved.

Measurements: CL: 1.04–1.17 mm; PL: 0.33–0.38 mm, PW: 0.39–0.44 mm; EL: 0.72–0.78 mm, EW: 0.49–0.57 mm.

Distribution.

China. Only known from the type locality in Luodian County, Qiannan Buyi and Miao Autonomous Prefecture, Guizhou Province.

Biology.

All adults were collected from gravel on the bottom of a small stream in a ravine (Fig. 6 A – C ).

Etymology.

The specific epithet “ luodianensis ” refers to the type locality, Luodian County, Qiannan Buyi and Miao Autonomous Prefecture, Guizhou Province; the name is treated as an adjective.

Comparative diagnosis.

The new species can be easily distinguished from other Sinonychus species by its scaly plastron setae, and males by the aedeagus with very long, thread-like sclerotization extending from the middle of the median lobe and exceeding its apex.

Figures

Figure 1. A dorsal habitus of Sinonychus lipinae sp. nov. B dorsal habitus of S. luodianensis sp. nov. C antenna of S. lipinae sp. nov. D antenna of S. luodianensis sp. nov. Scale bars: 0.5 mm (A, B); 0.05 mm (C, D).

Figure 3. Diagnostic features of Sinonychus luodianensis sp. nov. A head B pronotum C prosternal process D metaventrite E abdomen F elytron. Scale bars: 0.1 mm (A); 0.2 mm (B – F).

Figure 4. Genital features of Sinonychus species: A – G Sinonychus lipinae sp. nov. H – N, Sinonychus luodianensis sp. nov. A, H aedeagus, dorsal view B, J ditto, ventral C, I ditto, median lobe D, K ditto lateral view E, L sternite IX F, M ovipositor G, N ditto, apical part. Scale bars: 0.05 mm (G, N); 0.1 mm (A – F, H – M).

Figure 6. Habitat of Sinonychus luodianensis sp. nov. at the type locality A general environment B microenvironment C living adult.