Tribasodites vertexalis Yin 2022, sp. nov.
Creators: name: Yin, Zi-Wei
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Tribasodites
Tribasodites vertexalis

description: Tribasodites vertexalis sp. nov.
(Figs 73, 86C, 100B)
Chinese common name: ḔĦûḃà甲
Type material (1 ex.). HOLOTYPE: CHINA: ♂, ‘ China: Xizang, Mêdog County, 96K, 1460 m, 29°35’0.81”N, 95°27’58.26”E, 17.iii.2017, X.-B. Song leg. [ƱẪẸṘ 96K]’ (SNUC).
Diagnosis. Male. Body length 2.40 mm. Head rounded triangular, as broad as pronotum, tempus moderately long, vertex and frons strongly modified, each with large projection at middle; antenna lacking modifications. Pronotum with laterally carinate median and lateral longitudinal sulci, discal carinae composed row of two small discal and one large antebasal spine; lateral margin denticulate at anterior half, with distinct marginal spine. Discal stria of elytron shallow and long, extending posteriorly to apical 1/4 of elytral length; disc finely punctate. Fore legs simple; mesotrochanter with apically curved ventral spine, mesotibia with distinct apical spine; metatrochanter with broad, curved ventral projection. Aedeagus strongly asymmetric, median lobe constricted at base, ventral stalk strongly broad at middle, dorsal lobe weakly sclerotized, parameres flattened, membranous.
Description. Male. Body (Fig. 73A) length 2.40 mm; color reddish-brown, tarsi and mouthparts lighter. Dorsal surface of body covered with relatively dense pubescence.
Head (Fig. 73B) rounded triangular, much wider than long, length 0.48 mm, width across eyes 0.59 mm; vertex with large projection at middle, area anterior and lateral projection impressed and with pair of nude foveae, with tufts of setae at anterolateral margins of impression, postocular area with oval patch covered by dense, short setae; frons anteriorly demarcated from clypeus by complete frontal-clypeal ridge, which merged at middle and extending anteriorly to apex of clypeus, with strongly raised tubercle covered by long posteriorly pointed setae at middle; clypeus with smooth surface, its entire anterior margin carinate and raised; ocular-mandibular carina complete, carina branched below eye, extended ventrally and then anteriorly to posteroventral articulation of mandible. Venter with rough surface; small gular foveae (posterior tentorial pits) originating from shared oval opening, with thin median carina extending from opening anteriorly to mouthparts. Compound eyes prominent, composed of approximately 55 ommatidia. Antenna lacking modification, length 1.26 mm, club (Fig. 73C) loosely formed by enlarged apical three antennomeres; antennomere 1 thick, subcylindrical, 2–7 each slightly elongate, sub-moniliform, 8 smallest, 9 much larger than 8, elongate, 10 slightly broader and as long as 9, 11 largest, approximately as long as 9 and 10 combined, sub-fusiform, with indistinct line separating apical 2/5 from basal 3/5.
Pronotum (Fig. 73B) slightly wider than long, length 0.53 mm, width 0.58 mm, widest at middle; lateral margins rounded at middle, convergent apically and parallel at basal 1/4; disc moderately convex, finely punctate, median longitudinal sulcus with carinate sides, followed posteriorly by oval impression and short mediobasal carina, with pair of mesally carinate lateral longitudinal sulci, discal carinae composed of row of two distinct discal and one large antebasal spine; lateral margin with large marginal and five to six smaller spines; lateral antebasal foveae small and asetose; with small outer and inner pair of basolateral foveae. Prosternum with anterior part longer than coxal part, with small lateral procoxal foveae; thin hypomeral ridge complete, extending from base to middle of anterior part, with punctiform lateral antebasal hypomeral pit; margin of coxal cavity broadly carinate.
Elytra wider than long, length 0.73 mm, width 0.97 mm, widest at middle, narrowing form middle towards apex; each elytron with three large, asetose basal foveae; discal stria shallow and long, extending posteriorly from outer basal fovea to apical 1/4 of elytral length; humerus broadly prominent, with small denticle, subhumeral fovea small, carinate marginal stria extending from fovea to posterior margin of elytron.
Mesoventrite short, demarcated from metaventrite by transverse carinae; median mesoventral foveae relatively broadly separated, large lateral mesoventral foveae not forked internally, with short mesoventral process. Metaventrite slightly prominent admesally, impressed at middle, with well-developed lateral mesocoxal and two lateral metaventral foveae, posterior margin with small and narrow split at middle. Marginal carina of meso- and metaventrite complete.
Legs moderately elongate; protrochanter with exceptionally long seta on ventral margin; mesotrochanter with apically curved ventral spine (Fig. 73D), mesotibia (Fig. 73E) with triangular apical spine; metatrochanter (Fig. 73F) with broad, curved projection on ventral margin.
Abdomen widest at lateral margins of tergite 1 (IV), length 0.63 mm, width 0.88 mm. Tergite 1 (IV) less than twice as long as 2 (V), basal sulcus separated by one pair of mediobasal and two pairs of basolateral foveae, with pair of long discal carinae, inner marginal carina hardly oblique, outer one thicker, both complete; 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, 4 with small marginal tubercles, tergite 5 (VIII) semicircular, transverse, posterior margin roundly emarginate at middle. Sternite 2 (IV) with one pair of small mediobasal and three pairs of basolateral foveae; midlength of sternites 2–5 (IV–VII) gradually shorter, 3–4 each with two pairs of small basolateral foveae and small tubercle at middle, 5 with one pair of basolateral foveae, sternite 6 (VIII) transverse, posterior margin broadly emarginate, sternite 7 (IX) composed of several membranous structures.
Aedeagus (Fig. 73G–I) 0.35 mm long, strongly asymmetric; median lobe constricted at base, with rounded triangular foramen, ventral stalk strongly broad at middle, flattened apically and narrowing towards apex, dorsal lobe weakly sclerotized, extended to right side (in ventral view), parameres membranous, broad and plate-like.
Female. Unknown.
Comparative notes. Several different forms of aedeagi have been found within the possibly heterogenous Tribasodites. This species possesses an aedeagus of a form typical for the genera Hingstoniella, Besuchetaceus Yin & Li, and Sinotrisus Yin & Li, creating concerns about the relationships between these groups. At this moment no discrete character can be found to support a placement of this species elsewhere other than in Tribasodites. Among the Tibetan species, the habitus of T. vertexalis is relatively much stouter than the others, the male vertex is strongly modified with a large central excavation, and has lateral rounded areas covered by dense short setae. These characters in combination with the simple male antennae, the discal carina of the pronotum composed of three large spines, and the triangular apical spines of the mesotibiae readily separates this species from the others.
Distribution. Mêdog County, Tibet, SW China (Figs 86C, 100B).
Etymology. The species epithet refers to the strongly modified male vertex of this species.
description: Published as part of Yin, Zi-Wei, 2022, The Batrisini of Tibet: unveiling an enigmatic ant-loving beetle diversity at Earth's " Third Pole " (Coleoptera, Staphylinidae, Pselaphinae), pp. 1-211 in Zootaxa 5111 (1) on pages 171-173, DOI: 10.11646/zootaxa.5111.1.1, http://zenodo.org/record/6340729