Tribasodites prolixicornis, 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 : 166-168

Tribasodites prolixicornis sp. nov.

( Figs 71 , 86C , 93F, G )

Chinese common name: ḲƟûḃà甲

Type material ( 1 ex.). HOLOTYPE: CHINA: ♂, China: Xizang, Dinggyê County, Zhêntang Town , Ganma Zangbo Valley , 27°51’50”N, 87°24’24”E, 2400 m, 28.vi.2021, Z. Peng leg., ƱẪŤĠ县ĿƋWH玛Ẫ布河ě ’ ( SNUC).

Diagnosis. Male. Body length slightly over 2.1 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 small, indistinct foveae, with distinct mediobasal carina extending from head base anteriorly to level of anterior margin of eyes, with thin, faint lateral carina from base to posterior margin of antennal tubercle; antenna conspicuously elongate, lacking modifications, antennomeres each distinctly elongate. Pronotum with laterally carinate median and shallow lateral longitudinal sulci, with pair of longitudinal discal carinae, with pair of small antebasal and marginal spines. Discal stria of elytron shallow, extending posteriorly to apical 1/3 of elytral length; disc finely punctate. Mesotibia with small preapical tubercle; metafemur expanded before base, metatibia broadly and strongly sinuate along mesal margin. Aedeagus elongate, slightly asymmetric; median lobe with broad basal capsule and foramen, ventral stalk fusing with dorsal lobe at latter’s base, parameres broad, membranous.

Description. Male. Body ( Fig. 71A ) length 2.16 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.

Head ( Fig. 71B ) sub-rounded at base, as long as broad, length 0.49 mm, width across eyes 0.48 mm; vertex smooth, with shallow reversed U-shaped impression, vertexal foveae (dorsal tentorial pits) asetose, small, mediobasal carina distinct, extending from head base anteriorly to level of anterior margin of eyes, lateral carina thin, faint; posterolateral margin rounded; frons anteriorly demarcated from clypeus by faint 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, branched below eye, extended ventrally and then anteriorly to posteroventral articulation of mandible. Venter with granulate surface; small gular foveae (posterior tentorial pits) in single oval pit, with thin median carina extending from opening anteriorly to mouthparts. Compound eyes prominent, composed of approximately 45 ommatidia. Antenna elongate, length 1.58 mm, indistinct club formed by slightly enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, antennomeres each markedly elongate, 8 shortest, 9 much wider and longer than 8, cylindrical, 10 slightly wider than 9, broadened at apical 1/2, 11 largest, slightly shorter than 9 and 10 combined, sub-conical, anterolateral margin impressed.

Pronotum ( Fig. 71B ) approximately as long as wide, length 0.48 mm, width 0.46 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. 71C ) avoid additional spines, with thin lateral longitudinal sulci; with pairs of small antebasal and marginal spines; lateral antebasal foveae small and asetose; 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 shallow antebasal impression; margin of coxal cavity slightly carinate.

Elytra slightly wider than long, length 0.68 mm, width 0.70 mm; each elytron with three moderately large, asetose basal foveae; discal stria extending posteriorly from outer basal fovea to 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 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 apex; mesotibia ( Fig. 71D ) with small preapical tubercle; metatrochanter ( Fig. 71E ) with long curved ventral protuberance with long setae near base and setose apex, metafemur ( Fig. 71F ) strongly and broadly sinuate at mesal margin, covered with setae that are longer than those of pro- and mesofemur.

Abdomen constricted near base, widest at lateral margins of tergite 1 (IV), length 0.59 mm, width 0.63 mm. Tergite 1 (IV) slightly longer than 2 and 3 (V and VI) combined, lacking basal sulcus, with one pair of mediobasal and two pairs of basolateral foveae, pair of thin and short discal carinae and 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 narrowly emarginate at middle. Sternite 2 (IV) with one pair of mediobasal and three pairs of basolateral foveae, lateral two pairs in large sockets, lateral carina absent; midlength of sternite 2 more than twice length of 3 (V), 3 as long as 4 (VI), 5 (VII) slightly longer than 4, sternites 3–5 each with one pair of small basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, convex at middle, sternite 7 (IX) ( Fig. 71G ) composed of pair of triangular, membranous structures.

Aedeagus ( Fig. 71H–J ) 0.38 mm long, slightly asymmetric, elongate; median lobe with broad basal capsule and large foramen, basoventral projection long and enlarged, ventral stalk broad at base and apex, narrowed at middle; dorsal lobe fusing with median lobe at base, elongate, moderately curved, moderately expanded apically and with rounded apex, parameres fused, broad and flattened, membranous.

Female. Unknown.

Comparative notes. This species is allied with a group of species centered on T. dilophus and appears to be morphologically most similar to T. grandiceps in the lack of additional spines along the discal carinae of the pronotum, the presence of a preapical tubercle on the male mesotibiae, and the expanded male metafemora. Tribasodites prolixicornis can be readily separated from T. grandiceps by the relatively much longer antennae, the head being only slightly wider than pronotum and with more strongly prominent eyes, the much longer elytra, the different form of the male metafemoral expansion, and the dorsal lobe of the aedeagus only slightly curved at the apical portion (strongly twisted in T. grandiceps ).

Distribution. Dinggyê County, Tibet, SW China ( Figs 86C , 93F, G ).

Etymology. The specific name is combined from ‘ prolixus (stretched out, extended)’ and ‘ cornis (horned)’, referring to the markedly elongate antennae of this species.

Figures

FIGURE 71. Morphology of Tribasodites prolixicornis sp. nov., male. A. Dorsal habitus. B. Head and pronotum. C. Pronotum, in dorsolateral view. D. Apex of mesotibia. E. Metatrochanter. F. Metafemur. 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, E, 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 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.