Tribasodites cellulanus, 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 : 147-149

Tribasodites cellulanus sp. nov.

( Figs 63 , 85C , 92C )

Chinese common name: Ḵ士ûḃà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Nyalam County, Zhangmu , Lixin Village (ĒẾ 村), 27°57’21”N, 85°58’41”E, leaf litter, sifted, 2400–2600 m, 27.vii.2010, Jian-Qing Zhu leg.’ ( SNUC).

Diagnosis. Male. Body length approximately 2.2 mm. Head subtruncate at base, slightly narrower than pronotum, tempus moderately short, rounded at posterolateral angle, vertex with transverse impression anteriorly, with relatively large, setose foveae, with distinct mediobasal carina extending from near head base anteriorly slightly at level of middle length of eyes, with distinct oblique lateral carina from base to posterior margin of antennal tubercle; antenna elongate, antennomere 11 with short broad projection at base. Pronotum with laterally carinate median and lateral longitudinal sulci, with pair of discal carinae, with two pairs of antebasal and distinct marginal spines. Discal stria of elytron long, extending posteriorly to more than apical 3/4 of elytral length; disc finely punctate.All trochanters with ventral spine or projection, mesotibia simple. Aedeagus strongly asymmetric; median lobe with extended basal capsule and large foramen, ventral stalk in lateral view elongate and sinuate, dorsal lobe large, plate-like, with elongate sclerite broadly forked at apex.

Description. Male. Body ( Fig. 63A ) length 2.19 mm; head, pronotum, abdomen dark reddish-brown, legs, antennae and elytra reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.

Head ( Fig. 63B ) sub-rectangular at base, much wider than long, length 0.43 mm, width across eyes 0.52 mm; vertex smooth, with broad transverse impression demarcating from frons, vertexal foveae (dorsal tentorial pits) setose, relatively large, mediobasal carina distinct, extending from near head base anteriorly to slightly posterior to level of middle length of eyes, lateral carina distinct, curved, extending from head base to posterior margin of antennal tubercle; posterolateral margin rounded; frons weakly impressed between large, moderately raised antennal tubercles, anteriorly demarcated from clypeus by frontal-clypeal ridge; clypeus with smooth surface, short, 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) fused, originating from shared oval opening, with thin median carina extending from opening anteriorly to mouthparts. Compound eyes moderately prominent, composed of approximately 35 ommatidia. Antenna moderately elongate, length 1.13 mm, distinct club ( Fig. 63C ) formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–7 each slightly elongate to as long as wide, 8 smallest, moniliform, 9 much wider than 8, transverse, 10 much broader and slightly longer than 9, 11 largest, approximately as long as than 8–10 combined, with short, subtriangular projection at base of mesal margin, apex of projection with small setose tuft.

Pronotum ( Fig. 63B ) slightly wider than long, length 0.50 mm, width 0.56 mm, widest at middle; lateral margins rounded, smooth at apical 1/2, convergent basally; disc slightly convex, finely punctate, broad median longitudinal sulcus with carinate sides, posteriorly confluent with oval antebasal impression and short mediobasal carina, with pair of curved discal carinae and lateral longitudinal sulci; with two pairs of blunt antebasal and distinct 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; thick hypomeral ridge extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity broadly carinate.

Elytra much wider than long, length 0.57 mm, width 0.76 mm; each elytron with three large, asetose basal foveae; long discal stria extending posteriorly from outer basal fovea to more than 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 median opening, large lateral mesoventral foveae not forked internally, with short mesoventral process, with complete marginal stria. Metaventrite prominent admesally, inclined towards middle, with well-developed lateral mesocoxal foveae, two lateral metaventral foveae moving medially and in large, setose shared impression; posterior margin roundly emarginate at middle, lacking split.

Legs elongate; procoxa with exceptionally long seta at base, protrochanter ( Fig. 63D ) with small ventral spine, protibia with tiny preapical denticle at mesal margin; mesotrochanter ( Fig. 63E ) with long ventral spine, mesotibia simple; metatrochanter ( Fig. 63F ) with long, strongly curved ventral projection at apex, metatibia lacking tuft of long setae at apex.

Abdomen widest at lateral margins of tergite 1 (IV), length 0.71 mm, width 0.75 mm. Tergite 1 (IV) more than twice as long as 2 (V), lacking basal sulcus, with broadly separated 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 roundly 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 and 5 with two pairs of small basolateral foveae and short lateral carinae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) ( Fig. 63G ) weakly sclerotized, slightly oval.

Aedeagus ( Fig. 63H, I ) 0.51 mm long, strongly asymmetric, elongate; median lobe with large extended basal capsule and large, elongate foramen, ventral stalk in dorsal view broad, laterally sinuate and narrowing towards apex; dorsal lobe large, plate-like, with elongate sclerite broadly forked at apex; parameres reduced to single broad membrane.

Female. Unknown.

Comparative notes. This species shares with T. bari , T. constrictus , T. gyirong , and T. pugiunculus modified male antennomeres 11 and similar aedeagal forms, and is sympatric with T. pugiunculus near Zhangmu. The male of Tribasodites cellulanus can be distinguished from that of T. pugiunculus by the shorter elytra, the more robust antennomeres 11, the lack of a long apical spine on the mesotibia, as well as a different aedeagal form. This combination of characters also separates this species from all other similar congeners.

Distribution. Nyalam County, Tibet, SW China ( Figs 85C , 92C ).

Etymology. The species epithet ‘ cellulanus (hermit, recluse)’ is a Latin noun referring to the rarity of this species.

Figures

FIGURE 63. Morphology of Tribasodites cellulanus sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Antennomeres 9–11. D. Protrochanter. E. Mesotrochanter. F. Metatrochanter. G. Sternite 7 (IX). H, I. Aedeagus, lateral (H) and ventral (I). 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.

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 92. Environment of Zhangmu Valley (樟木沟). Environment of Youyiqiao (友谊桥) (A, B), Lixin Village (ĒẾ村) (C) and Qu Township (DZ乡) (D). Photo Credit: A, B by Jian-Qing Zhu; C, D by Wen-Xuan Bi.