Tribasodites mirabilis, 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 : 164-166

Tribasodites mirabilis sp. nov.

( Figs 70 , 86B , 93E )

Chinese common name: OiAEûḃà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Dinggyê County, Zhêntang Town , Xiuxiongma Vill., 27°54’11”N, 87°22’42”E, 2700–3000 m, 25.vi.2021, Z. Peng, Z. Yin & W. Zhang leg., ƱẪU喀NJŤĠ县Ŀ ƋWšŏ玛村 ’ ( SNUC).

Diagnosis. Male. Body length 2.06 mm. Head sub-rounded at base, approximately as wide as pronotum, tempus moderately long, with rounded posterolateral margin, vertex with shallow reversed U-shaped impression, with moderately large, setose foveae, with distinct mediobasal carina extending from head base anteriorly to before level of anterior margin of eyes, with thin 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 distinct antebasal and small marginal spines. Discal stria of elytron shallow, extending posteriorly before elytral midlength; disc finely punctate. Mesotibia with tiny preapical tubercle; metatrochanter with small protuberance on ventral margin, metafemur expanded before apex, metatibia with tuft of curved setae at apical 1/3. Aedeagus elongate, asymmetric; median lobe with large basal capsule and foramen, ventral stalk and dorsal lobe elongate, parameres broad, membranous.

Description. Male. Body ( Fig. 70A ) length 2.06 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.

Head ( Fig. 70B ) sub-rounded at base, as long as broad, length 0.45 mm, width across eyes 0.46 mm; vertex smooth, with shallow reversed U-shaped impression, vertexal foveae (dorsal tentorial pits) asetose, moderately large, mediobasal carina distinct, extending from head base anteriorly to slightly beyond level of anterior margin of eyes, lateral carina thin, shortly present at base; posterolateral margin rounded; frons anteriorly demarcated from clypeus by oblique frontal-clypeal ridge, 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, shortly branched below eye. Venter with smooth surface; small gular foveae (posterior tentorial pits) in single oval opening, with thin median carina extending from opening anteriorly to mouthparts. Compound eyes small, each composed of approximately 14 ommatidia. Antenna elongate, length 1.08 mm, indistinct club formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–7 each slightly elongate, 8 shortest, sub-moniliform, 9 much wider and longer than 8, subconical, 10 wider than 9, subconical, 11 largest, slightly longer than 9 and 10 combined, sub-conical, anteromesal margin impressed.

Pronotum ( Fig. 70B ) approximately as long as wide, length 0.46 mm, width 0.45 mm, widest at middle; lateral margins rounded at middle, convergent apically and basally; 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. 70C ) each composed of four distinct spines, with thin lateral longitudinal sulci; with pairs of distinct antebasal and small marginal spines; lateral antebasal foveae distinct and setose; with tiny 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 0.56 mm, width 0.69 mm; each elytron with three moderately large, asetose basal foveae; discal stria extending posteriorly from outer basal fovea to before elytral midlength; 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 setae at apex; mesotibia with tiny preapical tubercle; metatrochanter ( Fig. 70D ) with short curved ventral protuberance, metafemur ( Fig. 70E ) angularly expanded at apical 1/3, metatibia ( Fig. 70F ) concave at apical 2/5 of lateral margin, filled with tuft of long, curved setae.

Abdomen constricted at base, widest at lateral margins of tergite 1 (IV), length 0.57 mm, width 0.64 mm. Tergite 1 (IV) approximately as long as 2 and 3 (V and VI) combined, lacking basal sulcus, with one mediobasal and two pairs of basolateral foveae, with complete thin inner and thickened outer marginal carinae; tergite 2 (V) slightly longer than 3 (VI), 4 (VII) shorter than tergites 2 and 3 combined, 2–4 each with one pair of small basolateral foveae and pair of thin marginal carinae; tergite 5 (VIII) semicircular, transverse, posterior margin angularly emarginate at middle. Sternite 2 (IV) with one pair of mediobasal and two pairs of basolateral foveae, lateral carina absent; midlength of sternites 2–4 (IV–VI) gradually shorter, 5 (VII) slightly longer than 4, sternites 3 and 4 each with three pairs and 5 with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, convex at middle, sternite 7 (IX) ( Fig. 70G ) composed of pair of triangular, membranous structures.

Aedeagus ( Fig. 70H–J ) 0.37 mm long, asymmetric, elongate; median lobe with broad basal capsule and large foramen, ventral stalk markedly expanded basolaterally and narrowing apically; dorsal lobe also broad at base and narrowing towards membranous apex, parameres fused, broad and flattened, membranous.

Female. Unknown.

Comparative notes. This species is allied with T. dilophus , T. grandiceps , T. kiypu , T. prolixicornis , and T. yatung by the long, rounded postocular margins, the simple and elongate male antennae, and an elongate and slender aedeagus (except for T. dilophus , which has a much broader aedeagus). The male of T. mirabilis can be readily separated from that of these congeners by the strongly modified tibiae alone, as well as by the unique form of the aedeagus.

Distribution. Dinggyê County, Tibet, SW China ( Figs 86B , 93E ).

Etymology. The specific epithet ‘ mirabilis (wonderful, astonishing)’ is a Latin adjective referring to the remarkably modified male hind legs of this species.

Figures

FIGURE 70. Morphology of Tribasodites mirabilis sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Pronotum, in dorsolateral view. D. Metatrochanter. E. Metafemur. F. Metatibia. 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; 0.2 mm in C, E, F; 0.1 mm D, G–J.

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 93. Environment of and collecting sites at Zhêntang Valley (ĿƋ沟). Slopes at altitudes of 3700 m (A), 4000 m (B), and 3050 m (C). D. Nadang Village (Ḅ当村). E. Road to Xiuxiongma Village (šŏ玛村). F, G. Environment of Ganma Zangbo Valley (HḼẪ布河ě). Photo Credit: F, G by Zhong Peng.