Tribasodites yatung, Yin, 2022

Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth’s “ Third Pole ” (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5111 (1), pp. 1-211 : 173-175

Tribasodites yatung sp. nov.

( Figs 74 , 86C , 94A )

Chinese common name: 亚东ûḃà甲

Type material ( 2 exx.). HOLOTYPE: CHINA: ♂, ‘China: Xizang, Yatung County, Xiayadong Township , 27°25’57”N, 88°56’44”E, 3400 m, 18.viii.2010, Jian-Qing Zhu leg. [ƱẪ亚东县T亚东乡]’ ( SNUC). PARATYPE: CHINA: 1 ♂, same data as that of holotype ( SNUC).

Diagnosis. Male. Body length approximately 2.0 mm. Head sub-rounded at base, approximately as wide as pronotum, tempus moderately long, with rounded posterolateral margin, vertex lacking sulcus, with relatively large, asetose foveae, with distinct mediobasal carina extending from head base anteriorly to level of anterior margin of eyes, with distinct lateral carina from base to posterior margin of antennal tubercle; antenna elongate, lacking modifications, antennomeres slightly elongate. Pronotum with laterally carinate median and shallow lateral longitudinal sulci, with pair of longitudinal discal carinae composed of spines, with pair of large antebasal and small marginal spines. Discal stria of elytron shallow, extending posteriorly to pass half of elytral length; disc finely punctate. Mesotrochanter with distinct ventral spine, mesotibia with triangular projection at apex; metatrochanter with long protuberance on ventral margin. Aedeagus elongate, asymmetric; median lobe with large basal capsule and broad foramen, ventral stalk and dorsal lobe extremely elongate, parameres broad, membranous.

Description. Male. Body ( Fig. 74A ) length 1.97–2.13 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.

Head ( Fig. 74B ) sub-rounded at base, slightly broader than long, length 0.40–0.44 mm, width across eyes 0.44– 0.46 mm; vertex smooth, lacking sulcus, vertexal foveae (dorsal tentorial pits) asetose, relatively large, mediobasal carina distinct, extending from head base anteriorly to slightly beyond level of anterior margin of eyes, lateral carina distinct, extending from base to posterior margin of antennal tubercle; posterolateral margin rounded; 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 carina complete. Venter with smooth surface; small gular foveae (posterior tentorial pits) originating from shared oval opening, with thin median carina extending from opening anteriorly to mouthparts. Compound eyes prominent, composed of approximately 20 ommatidia. Antenna elongate, length 1.00– 1.1 mm, indistinct club formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each slightly elongate, 8 shortest, 9 much wider and longer than 8, subconical, 10 shorter than 9, subconical, 11 largest, slightly longer than 9 and 10 combined, subfusiform, impressed at anteromesal margin.

Pronotum ( Fig. 74B ) approximately as long as wide, length 0.43–0.47 mm, width 0.42–0.44 mm, widest at middle; lateral margins rounded at middle, convergent apically and sub-parallel at basal 1/4; disc slightly convex, finely punctate, thin median longitudinal sulcus with slightly carinate margins, posteriorly confluent with oval antebasal impression and short mediobasal carina, pair of discal longitudinal carinae ( Fig. 74C ) each composed of five distinct spines, with thin lateral longitudinal sulci; with pairs of large antebasal and small marginal spines; lateral antebasal foveae small and setose; with small outer and inner pair of basolateral foveae. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; distinct hypomeral ridge extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity slightly carinate.

Elytra much wider than long, length 0.59–0.61 mm, width 0.71–0.72 mm; each elytron with three moderately large, asetose basal foveae; discal stria extending posteriorly from outer basal fovea to pass half of elytral length; humerus denticulate, subhumeral fovea present, carinate marginal stria extending from fovea to posterior margin of elytron.

Mesoventrite short, demarcated from metaventrite by transverse carinae; median mesoventral foveae narrowly separated, originating from shared transverse opening, large lateral mesoventral foveae forked internally, with short mesoventral process, with complete marginal stria. Metaventrite moderately prominent admesally, inclined towards middle, with well-developed lateral mesocoxal foveae, with two lateral metaventral foveae, posterior margin roundly emarginate and with narrow split at middle.

Legs elongate; procoxa with exceptionally long seta at base; mesotrochanter ( Fig. 74D ) with blunt ventral spine, mesotibia ( Fig. 74E ) with large, rounded triangular apical projection; metatrochanter ( Fig. 74F ) with long, strongly curved ventral protuberance accompanied by thickened long seta, metatibia with short pencil-like tuft of setae at apex.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.54–0.62 mm, width 0.62–0.71 mm. Tergite 1 (IV) approximately twice as long as 2 (V), lacking basal sulcus, with one mediobasal and two pairs of basolateral foveae, with pair of broad, triangular discal carinae, marginal carinae complete, oblique inner carina thinner than outer one; tergite 2 (V) slightly longer than 3 (VI), with two pairs of small basolateral foveae and thin marginal carinae, 3 (VI) with one pair of small basolateral foveae and thin marginal carinae, 4 (VII) shorter than tergites 2 and 3 combined, with one pair of small basolateral foveae and thin, incomplete marginal carinae; 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, with short lateral carina; midlength of sternites 2–4 (IV–VI) gradually shorter, 5 (VII) slightly longer than 4, sternites 3–4 each with three pairs, two pairs and 5 with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) ( Fig. 74G ) composed of pair of triangular, membranous structures.

Aedeagus ( Fig. 74H–J ) 0.36 mm long, asymmetric, elongate; median lobe with broad basal capsule and large foramen, ventral stalk markedly narrowed and extremely elongate; dorsal lobe also extremely elongate at base approximately 7.5 times as broad as median lobe, narrowing apically and with rounded apex, parameres broad and flattened, membranous.

Female. Unknown.

Comparative notes. This species is allied with T. dilophus by the similar external morphology, and the pronotum with the discal carinae bearing five distinct spines and large antebasal spines. Tribasodites yatung can be separated by the relatively thicker antennae, the mesotibiae with large, rounded triangular projections at the apices (short apical spurs in T. dilophus ), the long and straight ventral protuberances of the metatrochanters (short and strongly curved projections in T. dilophus ), as well as an extremely elongate ventral stalk and dorsal lobe of the aedeagus (notably broad aedeagus in T. dilophus ).

Distribution. Yatung County, Tibet, SW China ( Figs 86C , 94A ).

Etymology. This species is named after Yatung County, where its type locality is situated.

Figures

FIGURE 74. Morphology of Tribasodites yatung sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Pronotum, in dorsolateral view. D. Mesotrochanter. E. Apex of mesotibia. F. Metatrochanter. G. Sternite 7 (IX). H–J. Aedeagus, dorsal (H), lateral (I) and ventral (J). Scale bars: 0.5 mm in A; 0.3 mm in B, F; 0.2 mm in C; 0.1 mm D–F, H–J, 0.05 mm in G.

FIGURE 86. Distribution of Tibetan Batrisini. A. Tribasodites dilophus sp. nov. (circle), T. elongatus sp. nov. (triangle) and T. grandiceps sp. nov. (square). B. T. gyirong sp. nov. (circle), T. kiypu sp. nov. (triangle) and T. mirabilis sp. nov. (square). C. T. prolixicornis sp. nov. (circle), T. Tribasodites pugiunculus sp. nov. (triangle) T. vertexalis sp. nov. (square) and T. yatung sp. nov. (diamond).

FIGURE 94. Environment of and collecting sites at Yatung Valley (亚东沟). General environment (A) of and collecting sites (B, C) at Xiayadong (T亚东). Photo Credit: A by Jian-Qing Zhu.