Tribasodites elongatus, 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 : 154-156

Tribasodites elongatus sp. nov.

( Figs 66 , 86A , 100C )

Chinese common name: ḞẦẆḃà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, ‘ China : Xizang, Zayü County, valley nr. Zhala Vill., 28°37’23.74”N, 97°21’8.10”E, 2190 m, 2019.vii.28, leaf litter / decomposing log, Z.-W. Yin leg.; [ƱẪ察ø县扎 Ń村ṉữ]’ ( SNUC).

Diagnosis. Male. Habitus elongate; body length 2.61 mm. Head slightly narrower than pronotum, vertex with long mediobasal and complete lateral carinae; antennomere 10 concave on ventral surface, antennomere 11 with large tubercle at base. Pronotum with broad and laterally carinate median longitudinal sulcus, one pair of discal carinae and one pair of lateral sulci, with discal, antebasal and lateral denticles. Discal stria of elytron long, extending posterior to apical 5/6 of elytral length. Protibia with preapical denticle, trochanters each with ventral spine or projection. Aedeagus strongly asymmetric; median lobe strongly, basal capsule extended, strongly constricted at base, ventral stalk narrowing and strongly curved apically; with large, plate-like dorsal lobe; parameres reduced.

Description. Male. Body ( Fig. 66A ) length 2.61 mm; color reddish-brown, head darkish brown, tarsi and mouthparts light reddish-brown. Dorsal surface of body covered with relatively short setae.

Head ( Fig. 66B ) sub-rounded at base, slight wider than long, length 0.43 mm, width across eyes 0.48 mm; vertex finely punctate, with setose vertexal foveae (dorsal tentorial pits), lacking U-shaped sulcus connecting foveae, lateral vertexal carinae extending from head base to base of antennal tubercles, mediobasal carina extending from head base to level of middle of eyes; antennal tubercles moderately raised; frons impressed between antennal tubercles, demarcated from clypeus by transverse carina; clypeus with smooth surface, anterior margin carinate and raised; ocular-mandibular. carinae distinct. Venter with gular foveae (posterior tentorial pits) merged into single pit, gular carina present only for short distance near mouthpart. Eyes moderately prominent, composed of approximately 35 ommatidia. Antenna elongate, length 1.25 mm; club formed by apical three antennomeres; antennomere 1 thick, subcylindrical, 2–8 each elongate, 8 smallest, 9 much larger than 8, subconical, 10 ( Fig. 66C, D ) much larger than 9, subconical, ventral surface broadly concave at base, 11 ( Fig. 66C, D ) largest, longer than 9 and 10 combined, truncate at base and narrowing apically, with large prominence at base, apex of prominence covered with short, thick setae.

Pronotum ( Fig. 66B ) slightly broader than long, length 0.48 mm, width 0.51 mm, widest anterior middle; lateral margins rounded, with distinct lateral denticles; disc slightly convex, finely punctate, with small discal and antebasal denticles, broad median longitudinal impression with carinate edges extending posteriorly to round mediobasal impression, followed by short basal carina, with one pair of discal carinae evenly curved and one pair of lateral longitudinal sulci extending to large lateral antebasal foveae; outer and inner pair of basolateral foveae distinct. Prosternum with anterior part as long as coxal part, hypomeral ridge extending from base to middle of anterior part; lateral procoxal foveae widely separated.

Elytra wider than long, length 0.65 mm, width 0.77 mm, lateral margins rounded; each elytron with three large, asetose basal foveae, inner two close; humerus weakly denticulate; thin discal stria extending from outer fovea to apical 5/6 of elytral length; small subhumeral fovea present, with carinate marginal stria extending from fovea to posterior margin of elytron.

Mesoventrite short, confluent with metaventrite; median mesoventral foveae widely separated, lateral mesoventral foveae extending internally below mesoventral ones. Metaventrite moderately impressed at middle, with well-developed lateral mesocoxal foveae and two indistinct lateral metaventral foveae at middle; posterior margin with small and narrow split at middle.

Legs elongate. Protrochanter ( Fig. 66E ) with short ventral spine, protibia ( Fig. 66F ) thickening apically, with triangular preapical denticle; mesotrochanter with ( Fig. 66G ) with ventral spine shorter than that of protrochanter; metatrochanter ( Fig. 66H ) with broad, curved ventral projection.

Abdomen elongate, widest at lateral margins of tergite 1 (IV), length 0.98 mm, width 0.68 mm. Tergite 1 (IV) moderately longer than tergite 2 (V), lacking discal carinae, short basal sulcus embraced by small mediobasal foveae, with one pair of large basolateral foveae, with thin and short inner marginal carina and complete, thick outer marginal carinae; tergites 2–4 (V–VII) subequal in length, each with basal sulcus between small basolateral foveae, tergite 5 (VIII) ( Fig. 66I ) broad, semicircular. Sternite 2 (IV) as long as sternites 3–4 (V–VI) at middle, with one pair of mediobasal and three pairs of basolateral foveae, midlength of sternites 2–4 gradually shortened; sternites 3 and 4 (V and VI) each with three pairs of basolateral foveae, sternite 5 (VII) with one pair of basolateral foveae, sternite 6 (VIII) ( Fig. 66J ) transverse, posterior margin broadly impressed, sternite 7 (IX) ( Fig. 66K ) oval, membranous.

Aedeagus ( Fig. 66L–N ) 0.58 mm long, strongly asymmetric; median lobe with large basal capsule and foramen, strongly constricted at base, ventral stalk strongly narrowed apically and strongly curved; dorsal lobe in dorsal view broad, plate-like; parameres reduced.

Female. Unknown.

Comparative notes. This species differs from all known congeners by the elongate body, a darker color of the head, the characteristic structures of male antennomere 10 and 11, as well as the form of the aedeagus.

Distribution. Zayü County, Tibet, SW China ( Figs 86A , 100C ).

Etymology. The specific epithet refers to the elongate body of this species.

Figures

FIGURE 66. Morphology of Tribasodites elongatus sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C, D. Antennomeres 9–11, in dorsal (C) and ventral view (D). E. Protrochanter and profemur. F. Protibia. G. Mesotrochanter and mesofemur. H. Metatrochanter and metafemur. I. Tergite 5 (VIII). J. Sternite 6 (VIII). K. Sternite 7 (IX). L–N. Aedeagus, dorsal (L), lateral (M) and ventral (N). Scale bars: 0.5 mm in A; 0.3 mm in B; 0.2 mm in C–J, L–N; 0.1 mm in K.

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 100. Environment of and collecting sites at Nyingchi area (A–E) and Chamdo (ăƀ) (F). A. 80K. B. 96K. C–E. Xiachayu (T察ø). F. pass of Jueba Mountain (ẅ巴山口), Markam (Ẽ康). Photo Credit: A by Zhong Peng; B by Xiao-Bin Song; F by Wen-Xuan Bi.