Tribasodites Jeannel 1960

Tribasodites Jeannel, 1960 Chinese common name: ûḃà甲¤ Tribasodites Jeannel, 1960: 411; Newton & Chandler 1989 (catalog); Sugaya & Maruyama 2003 (biological notes); Yin et al. 2011d, 2015b (cave species); Nomura & Aung 2020 (first record from Myanmar). Type species: Tribasodites antennalis Jeannel, 1960: 412 (original designation). This genus appears to be poorly defined by Jeannel (1960), since the presence of three basal elytra foveae and discal and marginal spines of the pronotum, as well as a relatively short tergite 1 (IV) of the abdomen is shared by many related genera. All species described here possess a lateral frontal fovea, which may potentially serve as a synapomorphy of the genus, or of a broader group that contains Tribasodites. Two major lineages occur in Tibet. The first contains six species that have modified antennomeres 11 (and often antennomeres 10), relatively short postocular margins, lack of a distinct row of discal spines on the pronotum, and the aedeagus with a plate-like dorsal lobe that partially surrounds the ventral stalk of the median lobe. The second lineage also includes six species, with all having elongate and simple antennae, the postocular margins of the head are relatively much longer, the pronotum usually bears two distinct rows of discal spines, and the aedeagus often has an elongate and slender ventral stalk of the median lobe and dorsal lobe. Tribasodites vertexalis, which possesses simple antennae, a modified vertex, and has a different aedeagal form, is also placed here. Numerous undescribed species possessing male sexual and aedeagal characters of varying forms have been seen from China and other areas of Asia. In Asia, Tribasodites contains many species that inhabit cave environments (Yin et al. 2011d, 2015b; Yin & Zhou 2018; Yin & He 2020), and others were commonly collected in decomposing logs or under bark of dead fallen trees, often with ants or termites (Nomura 1986; Zhao et al. 2010; Inoue & Maruyama 2020). However, there is no direct evidence, both ecologically or morphologically, indicating that these beetles are oblique myrmecophiles or termitophiles (Sugaya & Maruyama 2003), because many species of Tribasodites were often found without ants/ termites from the same habitats. Tribasodites hubeiensis Yin, Nomura & Li, originally described from material collected in two caves in southern Hubei, was found in a leaf litter sample at Maoer Mountain (á儿山) of Guangxi (W.-X. Zhang & Z.-W. Yin unpublished data), some 500 km south from the type locality. It is inferred that at least some of the cavernicolous Tribasodites are loosely associated with cave habitats. The fact that most of the described species have been taken only in caves likely reflects inadequate sampling efforts in the surrounding environments. Three species described here and that are sympatric in Gyirong were collected under barks on the same day: T, gyirong, T, kiypu, T, pugiunculus. The 13 Tibetan species may be distinguished by using the following key. Key to Tibetan species of Tribasodites (male) 1 Vertex and frons each with large median tubercle (Fig. 73B).................................... T. vertexalis sp. nov. - Vertex and frons simple, lacking modifications (Figs 62–72, 74)................................................ 2 2 Antennomere 10 and/or 11 modified; pronotum lacking row of spines along discal carina; aedeagus with broad dorsal lobe partially surrounding ventral stalk of median lobe (Figs 62–64, 66, 68, 72)........................................ 3 - Antenna simple, lacking modifications; pronotum often with row of spines along discal carina (spines lacking in two species that have modified metafemur); aedeagus usually with long and slender median and dorsal lobe (one species has broad dorsal lobe, but not partially surrounding ventral stalk) (Figs 65, 67, 69–71, 74)......................................... 8 3 Antennomere 10 lacking impression or cavity on ventral side.................................................. 4 - Antennomere 10 with impression or cavity on ventral side (Figs 62C, 66D, 68C, 72D).............................. 5 4 Pronotum with small marginal spines (Fig. 63B); mesofemur lacking spine on ventral margin........ T. cellulanus sp. nov. - Pronotum lacking marginal spines (Fig. 64B); mesofemur with long ventral spine (Fig. 64D) at base....................................................................................................... T. constrictus sp. nov. 5 Head dark brown, much darker than pronotum and elytra which are reddish-brown (Fig. 66A, B); antennomere 11 with broad, short prominence at base (Fig. 66C)....................................................... T. elongatus sp. nov. - Head, pronotum and elytra reddish-brown, unicolorous; antennomere 11 with distinctly much longer projection or protuberance at base.............................................................................................. 6 6 Antennomere 11 with markedly large and extended basal projection (Fig. 62C); mesotibia with indistinct apical tubercle............................................................................................. T. bari sp. nov. - Antennomere 11 with distinct conical basal protuberance; mesotibia with large, blade-like apical spine.................. 7 7 Body length greater than 2.5 mm (2.68–2.78 mm); anterior portion of vertex with distinct transverse impression (Fig. 68B); aedeagus (Fig. 68I, J)..................................................................... T. gyirong sp. nov. - Body length smaller than 2.5 mm (2.30–2.41 mm); anterior portion of vertex lacking distinct impression (Fig. 72B); aedeagus (Fig. 72I, J)........................................................................ T. pugiunculus sp. nov. 8 Body length greater than 2.5 mm (2.52–2.53 mm)............................................... T. kiypu sp. nov. - Body length smaller than 2.2 mm ......................................................................... 9 9 Metatibia expanded and with curved setose tuft on dorsal margin (Fig. 70F)........................ T. mirabilis sp. nov. - Metatibia simple..................................................................................... 10 10 Pronotum lacking row of spines along discal carina; metafemur modified........................................ 11 - Pronotum with row of spines along discal carina; metafemur simple............................................ 12 11 Head relatively broader, ratio (length/width) 43:47, eyes weakly prominent (with 35 ommatidia); dorsal lobe of aedeagus strongly twisted at apex (Fig. 67H–J)..................................................... T. grandiceps sp. nov. - Head relatively longer, ratio (length/width) 49:48, eyes markedly prominent (with 45 ommatidia); dorsal lobe of aedeagus slightly curved at apex (Fig. 71H–J).................................................... T. prolixicornis sp. nov. 12 Dorsal lobe of aedeagus conspicuously broad in dorsal view (Fig. 65G)............................ T. dilophus sp. nov. - Dorsal lobe of aedeagus long and slender in dorsal view (Fig. 74H, J).............................. T. yatung sp. nov.

Topic: Subterranean biodiversity and taxonomy
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences