Tribasodites constrictus, 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 : 149-151

Tribasodites constrictus sp. nov.

( Figs 64 , 85C , 95A, B )

Chinese common name: 束aûḃà甲

Type material (9 exx.). HOLOTYPE: CHINA: ♂ , ‘ China: Xizang, Cona County, Lebu Valley , pass to Mama Vill., 27°50’16”N, 91°45’48”E, 2400–2700 m, 04.vii.2021, Z. Peng, Z. Yin & W. Zhang leg., ƱẪDZḄ县勒布沟Þ玛 乡 ’ ( SNUC) . PARATYPES: CHINA: 3 ♂♂, 5 ♀♀, same data as that of holotype ( SNUC) .

Diagnosis. Male. Body length slightly over 2.2 mm. Head subtruncate at base, slightly narrower than pronotum, tempus moderately short, rounded at posterolateral angle, vertex with incomplete reversed U-shaped sulcus connecting foveae, with relatively large, setose foveae, with distinct mediobasal carina extending from head base anteriorly to level of eye midlength, lateral carina absent; antenna elongate, antennomere 11 with thin, long basal projection. Pronotum with laterally carinate median and lateral longitudinal sulci, with pair of discal carinae, with large antebasal protuberance, lacking marginal spine. Elytra constricted at bases, discal stria thin and shallow, extending posteriorly to approximately apical 1/3 of elytral length; disc finely punctate. Mesotibia with small apical spine. Aedeagus strongly asymmetric; median lobe with extended basal capsule and elongate foramen, ventral stalk in lateral view deeply forked at apical portion, dorsal lobe large, plate-like, embracing median lobe. Female. Body length approximately 2.1 mm, antenna shorter than male, antenna and legs lacking modifications, genitalia as in Fig. 64J .

Description. Male. Body ( Fig. 64A ) length 2.22–2.27 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively long pubescence.

Head ( Fig. 64B ) roundly at base, much wider than long, length 0.40–0.42 mm, width across eyes 0.48–0.50 mm; vertex smooth, with incomplete reversed U-shaped sulcus connecting relatively large, setose vertexal foveae (dorsal tentorial pits), mediobasal carina distinct, extending from head base anteriorly to level of eye midlength, lateral carina absent; posterolateral margin rounded; frons impressed between large, moderately raised antennal tubercles, anteriorly confluent with clypeus; clypeus with smooth surface, its entire anterior margin strongly carinate and moderately raised; ocular-mandibular carina complete, carina branched below eye, extended ventrally and then anteriorly to posteroventral articulation of mandible. Venter with smooth surface; small gular foveae (posterior tentorial pits) originating from shared oval opening, median carina present only posterior mouthparts for short distance. Compound eyes prominent, composed of approximately 22 ommatidia. Antenna elongate, length 1.09–1.14 mm, indistinct club ( Fig. 64C ) formed by moderately enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each sub-moniliform, 7 distinctly enlarged, much longer than neighboring antennomeres, 9 slightly transverse, much wider than 8, 10 strongly transverse, much broader and approximately as long as 9, ventral surface lacking impression, 11 largest, longer than 9 and 10 combined, with distinct basoventral projection, apex of projection with elongate setae.

Pronotum ( Fig. 64B ) slightly wider than long, length 0.50–0.51 mm, width 0.53 mm, widest at middle; lateral margins rounded, convergent anteriorly and evenly narrowing posteriorly for basal 1/3; disc slightly convex, finely punctate, broad median longitudinal sulcus with carinate sides, posteriorly confluent with large, oval antebasal impression and short mediobasal carina, with pair of discal carinae and lateral longitudinal sulci; with large pair of antebasal protuberances, lacking marginal spines; lateral antebasal foveae large and setose; with distinct outer and inner pair of basolateral foveae. Prosternum with anterior part slightly longer than coxal part, with small lateral procoxal foveae; thick hypomeral ridge extending from base to middle of anterior part, with anterior and lateral antebasal hypomeral impressions; margin of coxal cavity carinate.

Elytra basally constricted, much wider than long, length 0.60–0.61 mm, width 0.74–0.75 mm; each elytron with three moderately large, asetose basal foveae; long discal stria extending posteriorly from outer basal fovea to approximately apical 1/3 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 not forked internally, with short mesoventral process, with complete marginal stria. Metaventrite moderately prominent admesally, inclined towards middle, with well-developed lateral mesocoxal foveae and pair of lateral metaventral foveae; posterior margin roundly emarginate at middle, with narrow split.

Legs elongate; procoxa with exceptionally long seta at base, protibia with tiny preapical denticle at mesal margin; mesotrochanter ( Fig. 64D ) with short ventral tubercle, mesofemur ( Fig. 64D ) with long ventral spine at base, mesotibia ( Fig. 64E ) with small apical protuberance; metatrochanter ( Fig. 64F ) with large, long ventral projection strongly curved at apex.

Abdomen narrowed before base, widest at lateral margins of tergite 1 (IV), length 0.73–0.76 mm, width 0.75– 0.80 mm. Tergite 1 (IV) approximately 1.6 times as long as 2 (V), lacking basal sulcus, with large mediobasal and one pair of basolateral foveae, with pair of short discal carinae, marginal carinae complete, oblique inner carina thinner than outer one; tergite 2 (V) slightly longer than 3 (VI), 4 (VII) shorter than tergites 2 and 3 combined; tergites 2–4 (V–VII) each with one pair of basolateral foveae, tergite 5 (VIII) semicircular, transverse, posterior margin narrowly emarginate at middle. Sternite 2 (IV) with one pair of mediobasal and two pairs of basolateral foveae, lacking lateral carina; midlength of sternites 2–4 (IV–VI) gradually shorter, 5 (VII) slightly longer than 4, 3 and 4 each with three pairs and 5 with one pair of basolateral foveae, lacking lateral carinae, sternite 6 (VIII) longer than 3–5 combined, medially impressed, posterior margin broadly emarginate and slightly convex at middle, sternite 7 (IX) ( Fig. 64G ) weakly sclerotized, slightly oval.

Aedeagus ( Fig. 64H, I ) 0.58 mm long, strongly asymmetric, elongate; median lobe with large extended basal capsule and elongate foramen, ventral stalk in lateral view deeply forked into two elongate lobes; dorsal lobe large, plate-like, embracing median lobe, with rounded apex; parameres short, membranous.

Female. Similar to male in external morphology; antenna slightly shorter than male; antenna and legs lacking modifications; each compound eye composed of approximately 15 ommatidia; tergite 1 (IV) with only one pair of basolateral foveae, lacking mediobasal foveae. Measurements (as for male): body length 2.08–2.10 mm; length/width of head 0.40/ 0.48–0.49 mm, pronotum 0.49/ 0.52–0.54 mm, elytra 0.53–0.54/ 0.70 mm; abdomen 0.71– 0.77/ 0.72 mm; length of antenna 0.96–0.97 mm; genitalia weakly sclerotized ( Fig. 64J ), with pair of membranous lateral plates, maximum width 0.32 mm.

Comparative notes. The male of this species is close to those of T. bari , T. gyirong , and T. pugiunculus by antennomeres 11 having a basal projection, and a similar general form of the aedeagus. Tribasodites constrictus differs in the lack of marginal spines on the pronotum, the relatively small and basally constricted elytra, the presence of a long mesofemoral spine, and a different aedeagal form.

Distribution. Cona County, Tibet, SW China ( Figs 85C , 95A, B ).

Etymology. The specific epithet ‘ cônstrictus (bound together, tied up)’ is a Latin adjective suggested by the constricted elytral base of this species.

Figures

FIGURE 64. Morphology of Tribasodites constrictus sp. nov. (A–I. Male. J. Female). A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 9–11. D. Mesotrochanter and base of mesofemur. E. Apex of mesotibia. F. Metatrochanter. G. Sternite 7 (IX). H, I. Aedeagus, lateral (H) and ventral (I). J. Genitalia. Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C, H, I; 0.1 mm in D–G, J.

FIGURE 85. Distribution of Tibetan Batrisini. A. Sathytes xizangensis Yin & Shen (circle) and S. yigongensis sp. nov. (cross). B. Tangius glabellus Yin & Li. C. Tribasodites bari sp. nov. (circle), T. cellulanus sp. nov. (triangle) and T. constrictus sp. nov. (square).

FIGURE 95. Environment of and collecting sites at Lebu Valley (勒布沟). Forests at 2400 m (A, B), and 3650 m (C, D).