Tribasodites pectoralis, Zhang & Yin, 2025

Zhang, Yong-Qin & Yin, Zi-Wei, 2025, The ant-like litter beetle fauna from the Wumenshan National Nature Reserve, China, with description of eight new species (Staphylinidae: Pselaphinae), European Journal of Taxonomy 1007, pp. 133-162 : 150-153

Tribasodites pectoralis sp. nov.

Chinese common name: Ȇḃẘḃü甲 urn:lsid:zoobank.org:act:019B1E4E-9F7C-4630-A177-5DF0483D5ECC Fig. 6

Diagnosis

Male Body elongate, length approximately 2.2 mm. Head transversely suboval, subtruncate at base, slightly narrower than pronotum, tempora distinctly longer than eyes, rounded at posterolateral angles, vertex lacking sulcus, with small, asetose foveae, with distinct mediobasal carina extending from head base anteriorly to level of anterior margins of eyes, with distinct lateral carinae from head base to posterior margins of antennal tubercles; antenna elongate, with greatly modified antennomeres 10 and 11, 10 with large cavity on ventral surface, 11 with broad inner basal projection extended posteriorly. Pronotum with laterally carinate median and lateral longitudinal sulci, with pair of longitudinal discal carinae, with two pairs of antebasal tubercles and acute marginal spines. Discal striae extending posteriorly to approximately 6.6 /10 of elytral length. Mesotrochanter with tiny ventral tubercle, mesotibia with distinct apical spine. Aedeagus stout, asymmetric; ventral stalk broad at base and split at apical part, dorsal lobe plate-like, embracing ventral stalk, endophallus armature composed of mainly membranous structures.

Female

Body length approximately 2.2–2.3 mm. Antenna lacking modifications. Legs simple. Genital complex as in Fig. 6J .

Etymology

The specific epithet is derived from the Latin adjective ‘ pectoralis ’, meaning ‘of or pertaining to the chest’, referring to the protruding pronotal lateral margins of this species. The name is an adjective in the nominative singular.

Type material

Holotype

CHINA • ♂; Yunnan, Zhaotong City, Wumengshan Conservation Area, Miaoshan , Xiaocaoba ; 27°29′33″ N, 104°10′19″ E; 1709–1800 m a.s.l.; 20 Jul. 2022; Wei leg.; Ǖ南昭ª市乌®山小ẽữ, 魏 ǡ豪*; SNUC.

Paratypes

CHINA • 2 ♂♂, 1 ♀; same data as for holotype; SNUC • 1 ♀; Xiaoyanfang station ; 28°6′00″ N, 103°21′54″ E; 1878–2062 m a.s.l.; 13 Jul. 2022; SNUC .

Description

Male

BODY ( Fig. 6A ). Length 2.20–2.22 mm; colour reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.

HEAD ( Fig. 6B ). Subrounded at base, distinctly wider than long, length 0.45–0.46 mm, width 0.58 mm; vertex lacking sulcus, with small, asetose foveae (dorsal tentorial pits), mediobasal carina relatively long, extending from head subbase anteriorly to level of anterior margins of eyes, lateral carinae thick, extending from base to posterior margins of antennal tubercles; posterolateral margin roundly angulate; frons anteriorly demarcated from clypeus by oblique frontal-clypeal ridge, which merged at middle and extended anteriorly for short distance on clypeus, area between moderately raised antennal tubercles weakly impressed; clypeus with smooth surface, its entire anterior margin strongly carinate and moderately raised; ocular-mandibular carinae complete. Venter with smooth surface; small gular foveae (posterior tentorial pits) originating from shared transverse opening, with thin median carina extending from above opening to mouthparts. Compound eyes moderately small, each composed of approximately 30 small ommatidia. Antenna elongate, length 1.20–1.21 mm, distinct club ( Fig. 6C ) formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–7 each slightly elongate to as long as wide, 8 shortest, 9 obliquely expanded at apex, 10 ( Fig. 6D ) much broader and longer than 9, with large cavity on ventral surface, 11 largest, longer than 9 and 10 combined (33:23), with broad, posteriorly extended basal projection on mesal margin.

PRONOTUM ( Fig. 6B ). Much wider than long, length 0.48–0.49 mm, width 0.60–0.61 mm, widest anterior to middle; lateral margins rounded and extended, convergent apically and subparallel at approximately basal ¼; disc slightly convex, finely punctate, relatively broad median longitudinal sulcus with slightly carinate margins, posteriorly confluent with oval antebasal impression and short mediobasal carina, with pair of curved discal longitudinal carinae and lateral longitudinal sulci; with two pairs of short antebasal and acute marginal spines; lateral antebasal foveae small and asetose; with small outer and inner pair of basolateral foveae. Prosternum with basisternal (precoxal) portion slightly longer than procoxal rests, with small lateral procoxal foveae; distinct hypomeral grooves extending from base to middle of anterior parts, with pit-like lateral antebasal hypomeral impressions, hypomeral ridges close to margins of coxal cavities.

ELYTRA. Much wider than long, length 0.57–0.59 mm, width 0.76 mm; each elytron with three moderately large, asetose basal foveae; discal striae thin, extending posteriorly from outer basal foveae to approximately 7 /10 of elytral length; humeri slightly angulate, subhumeral foveae small, carinate marginal striae extending from foveae to posterior margins of elytra. Metathoracic wings fully developed.

MESOVENTRITE. Short, demarcated from metaventrite by oblique carinae lateral to mesocoxal cavities; median mesoventral foveae moderately separated, originating from shared suboval opening, large lateral mesoventral foveae forked internally, prepectus massive, collar-shaped; mesoventral intercoxal process short, apically blunt, marginal striae complete. Metaventrite slightly projected admesally, inclined towards middle, with large, setose lateral mesocoxal foveae, with two lateral metaventral foveae, metaventral intercoxal process with narrow split at middle.

LEGS. Moderately elongate; mesotrochanter ( Fig. 6E ) with tiny ventral tubercle, mesotibia ( Fig. 6F ) with distinct apical spine; mesal margin of metatibia with row of dense golden setae along apical ⅓.

ABDOMEN. Widest at lateral margins of tergite 1 (IV), length 0.73–0.74 mm, width 0.76–0.77 mm. Tergite 1 (IV) more than twice as long as 2 (V), thin basal sulcus interrupted by one pair of mediobasal and one pair of basolateral foveae, with pair of short, thick subtriangular discal carinae, oblique inner marginal carinae thin and complete, outer carinae present for basal ½; tergite 2 slightly longer than 3 but shorter than 4 (VII), 2–4 each with one pair of small basolateral foveae; tergite 5 (VIII) semicircular, transverse, posterior margin roundly emarginate at middle. Sternite 2 (IV) with one pair of mediobasal and two pairs of basolateral foveae, lacking lateral carinae; midlength of sternites 2–5 (IV–VII) gradually shorter, 3 and 4 each with three pairs, and 5 with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) ( Fig. 6G ) membranous, composed of pair of lateral membranes and suboval median plate.

AEDEAGUS ( Fig. 6H–I ). 0.48 mm long, dorso-ventrally strongly asymmetric; median lobe with large basal capsule, roundly triangular foramen and long and broad basoventral projection, ventral stalk broad at base, divided into two parts in apical portion, dorsal lobe plate-like, embracing ventral stalk; endophallus armature with mostly membranous structures; parameres fused, broad and flattened, membranous.

Female

Similar to male in external appearance; antenna slightly shorter, simple; legs lacking tubercles, spines or projections; each compound eye composed of approximately 15 ommatidia; humeri of elytra weakly raised; metathoracic wings reduced. Measurements (as for male): body length 2.23–2.29 mm; length/ width of head 0.46/ 0.59 mm, pronotum 0.45–0.48/ 0.56–0.58 mm, elytra 0.52–0.60/ 0.75–0.76 mm; abdomen 0.75–0.78/ 0.76–0.78 mm; length of antenna 1.06–1.14 mm; maximum width of genital complex ( Fig. 6J ) 0.30 mm.

Remarks

The greatly modified antennomeres 10 and 11, along with an aedeagus that bears a plate-like dorsal lobe, are common character states found within the genus. This species belongs to the Antennalis group as defined by Zhang & Yin (2024). A closely related species, T. bari Yin, 2022 , which exhibits a similar large projection at the base of male antennomere 11, is found in Xizang ( Yin 2022). However, T. pectoralis sp. nov. can be distinguished by its protruding lateral margins of the pronotum, which are equipped with acute marginal spines, as well as the unique structure of the aedeagus.

Distribution

Southwest China: Yunnan.

Figures

Fig. 6. Tribasodites pectoralis sp. nov. A–I. Holotype, ♂ (SNUC). J. Paratype, ♀ (SNUC). A. Dorsal habitus. B. Head and pronotum. C. Antennal club. D. Antennomere 10, ventral view. E. Mesotrochanter. F. Mesotibia. G. Sternite 7 (IX). H. Aedeagus, lateral view. I. Aedeagus, ventral view. J. Genitalia, ventral view. Scale bars: A = 0.5 mm; B = 0.3 mm; C, E–F = 0.2 mm; D, G–J = 0.1 mm.