Dayao gen. n. of the subtribe Tyrina (Coleoptera, Staphylinidae, Pselaphinae) from South China

Abstract Dayao pengzhongi gen. et sp. n. is described and illustrated based on the material collected in Guangxi Province, South China. The genus is placed in the oriental ‘Pselaphodes complex’ of genera of the subtribe Tyrina and its taxonomic placement is discussed.


Introduction
According to the most recent catalog of the tribe Tyrini (Hlaváč and Chandler 2005), 13 genera of the subtribe Tyrina have been known from the Oriental region. Eight of 13 genera centered on the genus Pselaphodes Westwood grouped as the 'Pselaphodes complex' of genera (Hlaváč 2002: 283): Indophodes Hlaváč, Labomimus Sharp, Lasinus Sharp, Linan Hlaváč, Nomuraius Hlaváč, Paralasinus Hlaváč & Nomura, Pselaphodes Westwood and Taiwanophodes Hlaváč. Determination of the generic placement within the group is usually based on the form of maxillary palpi, in the combination with the foveal pattern on the head, pronotum and thorax and the relative length of the scape.
Recently a small series of pselaphine was collected at Dayao Mountain in the Guangxi Province, South China. The pselaphines were identified as a member of the 'Pselaphodes complex' upon an examination of morphological characters, but eventually found not matching any current generic conception of a known genus. The aim of this paper is to describe the new genus and species in detail, provide illustrations of the diagnostic characters, and discuss its taxonomic placement.

Material and methods
All specimens were collected from the leaf litter of the forest floor by sifting. They were killed with ethyl acetate and then dried. Dissections were done in 75% ethanol. The genital organs and other dissected parts were mounted in Euparal (Chroma Gesellschaft Schmidt, Koengen, Germany) on plastic slides that were placed on the same pin as the specimen. Photos were taken by a Canon EOS 40D Camera mounted with an MP-E 65 mm Macro Photo Lens; line drawings were made using Adobe Illustrator CS2 based on the photos taken by a Canon G9 Camera mounted on an Olympus CX31 microscope.
A slash (/) is used to separate lines on the same label, and a double slash (//) is used to separate different labels on the same pin.
The following acronyms are used in the text:

AL
length of the abdomen; AW maximum width of the abdomen; BL length of the body (= HL + PL + EL + AL); EL length of the elytra, measured along sutural line; EW maximum width of the elytra; HL length of the head, measured from the anterior clypeal margin to the occipital constriction; HW width of the head across eyes; PL length of the pronotum along midline; PW maximum width of the pronotum; SHNU Shanghai Normal University, Shanghai, P. R. China.
The type series are deposited in the Insect Collections of Shanghai Normal University, Shanghai, China (SNUC).
Each elytron with two basal foveae; discal stria extending from second basal fovea and exceeding elytral midpoint.
Legs with tarsomeres simple, third tasomeres about 0.75 times as long as second tarsomeres.
Abdomen with tergite IV (visible tergite I) longer than V-VII combined; tergite IV with deep basal sulcus connecting basolateral foveae, lacking mediobasal fovea in sulcus; with long discal carinae; tergites V-VII each with basolateral foveae. Sternite IV largest, longer than V-VII combined, with deep basal sulcus densely covered by short setae.
Distribution. A single species in known from Dayao Mountain, Guangxi Province, South China.
Comparative notes. Dayao is placed near the genera of Pselaphodex complex with simple, linear tarsomere II not strongly bilobed, only slightly extending beneath tarsomere III: Paralasinus Hlaváč & Nomura, Lasinus Sharp, Linan Hlaváč, Indophodes Hlaváč, Labomimus Sharp and Pselaphodes Westwood. Among these genera, Dayao can be readily separated from Paralasinus and Lasinus by the clearly asymmetrical palpomeres II-IV, which are simple in both genera. Dayao is separated from Indophodes and Labomimus by the lack of a frontal and a median metaventral fovea; from Pselaphodes by the lack of a frontal fovea, the indistinct pronotal lateral antebasal foveae and the longer scape. The lack of a median metaventral fovea, the pronotum being finely punctate and the basal carinae of the tergite IV being much longer separate Dayao from Linan in which the median metaventral fovea is present, the pronotum is roughly and densely punctate and the basal carinae are much shorter.
Remarks. The published key to the world genera of Tyrini (Hlaváč and Chandler 2005) (Figs 4-5); median metaventral fovea absent (Fig. 6); long discal carinae of tergite IV distinct (Fig. 1) (Fig. 1). Length 2.95 mm (holotype). Head lengthily and bluntly triangular, HL 0.74 mm, HW 0.59 mm, with decumbent setae. Vertexal foveae located posterior to point level with posterior margin of eyes. Eyes prominent, each with about 35 facets. Antennae elongate (Fig. 2), scape longer than II-IV combined, II-IV each short, of same width, V-VIII each longer than II-IV, slightly narrower, of same width, shortened distally, antennomeres of club (Fig. 8) of about same width, IX slightly expanded laterally at basal third, X shorter than IX and XI, XI longer than IX, with rounded apex. Pronotum (Fig. 4) as long as wide, PL 0.66 mm, PW 0.64 mm, with 'Y'-shaped sulcus in anterior half, tufts of long golden setae at anterior margin of sulcus directed posteriorly. Elytra wider than long, EL 0.81 mm, EW 1.05 mm, lacking ridges. Venter (Fig. 6) with long metaventral process (Fig. 7) bent posteriorly near apex; metaventrite smooth, convex medially in apical half, with dense long setae at lateral portions and sparse minute setae at middle. Legs long, protibiae with small apical spines, pro-and mesofemora with distinct erect setae at ventral margins. Abdomen wider than long, AL 0.74 mm, AW 1.03 mm; discal carinae on tergite IV extending two-fifths of tergal length; tergite VIII transverse, narrowed apically in posterior half, with shallow median emargination, tergite IX (Fig. 10) semi-membranous, with apical portion strongly sclerotized; sternites VIII transverse. Aedeagus (Figs 11-13) length 0. 48 mm.  Etymology. The specific name recognizes the efforts of Zhong Peng in collecting the male holotype.