Six new species and a new record of Linan Hlaváč in China, with a key to species (Coleoptera, Staphylinidae, Pselaphinae)

Abstract Six new species of the genus Linan Hlaváč are described from central to southern China: L.arcitibialissp. n. (Hubei), L.denticulatussp. n. (Guizhou), L.divaricatussp. n. (Jiangxi), L.geneolatussp. n. (Guizhou), L.mangshanussp. n. (Hunan), and L.mulunensissp. n. (Guangxi), with illustrations of habitus and major diagnostic characters. Linanmegalobus Yin & Li, originally described from Guizhou, is newly recorded in Hubei. An updated key to and a distributional map of all 16 known species are provided.


Introduction
The pselaphine genus Linan Hlaváč belongs to the tribe Tyrini that is comprised of ten species predominantly distributed in China (with one species extending southwards to northern Thailand; Figure 11) (Hlaváč 2003;Yin et al. 2011Li 2012, 2013). Members are characterized by the head lacking or with indistinct vertexal and frontal foveae, laterally expanded or protuberant maxillary palpomeres II-IV, roughly punctate head and pronotum, lack of a transverse antebasal sulcus on the pronotum, and presence of a median metaventral fovea. Based on presence or absence of modifica-tion on male antennomeres IX-X, two species groups were defined . The current diversity of Linan remains underexplored. Here we report the discovery of six new species based on the material from various areas in China collected after 2012. The species number of Linan now rises to 16, we accordingly provide an updated identification key and distributional maps for the genus.

Material and methods
All material treated in this study is housed in the Insect Collection of Shanghai Normal University, Shanghai, China (SNUC).
The label data of the material are quoted verbatim, additional information is included in parentheses. Dissected parts were preserved in Euparal on plastic slides that were placed on the same pin with the specimen. The habitus image was taken using a Canon 5D Mark III camera in conjunction with a Canon MP-E 65mm f/2.8 1-5× Macro Lens, and a Canon MT-24EX Macro Twin Lite Flash was used as light source. Images of the morphological details were produced using a Canon G9 camera mounted to an Olympus CX31 microscope under transmitted light. Zerene Stacker (version 1.04) was used for image stacking. The base map was produced from http:// www.simplemappr.net/ (Shorthouse 2010). All images were optimized and grouped into plates in Adobe Photoshop CS5 Extended.
Distribution. China: Hubei ( Figure 11A). Etymology. The new specific epithet refers to the strongly arched mesotibiae. Comparative notes. The new species is placed as a member of the L. cardialisgroup based on the modified male antennomere IX. Linan arcitibialis is the only member of the group that exhibits a simple antennomere X. Combined with the unique form of antennomere IX and strongly arched mesotibia, males of this species can be readily separated from all other congeners at a quick glance. Diagnosis of male. Length 2.61mm; antennomeres IX-XI enlarged, lacking obvious modification; short metaventral processes narrowing toward apex, area above metacoxae projecting; protibia with distinct apical spine; metatrochanter with blunt, apically curved ventral projection.
Distribution. China: Guizhou ( Figure 11B). Etymology. The specific epithet refers to the large apical spine of the protibia. Comparative notes. Linan denticulatus is placed as a member of the L. chinensisgroup based on the unmodified male antennomeres IX-X, and externally resembles L. hujiayaoi Yin & Li from Guangxi. These two species share a similar form of the antennal club, short metaventral processes, and the blunt, apically curved ventral projection of the metatrochanter. They can be best separated by the much more distinct apical projection of the protibia, and median lobe of the aedeagus with a strongly narrowed apical part and much broader parameres in the new species. Diagnosis of male. Length 2.74-2.82 mm; antennomeres IX-X strongly modified, antennomere IX angulate at anterolateral corner, obliquely connecting with strongly transverse antennomere X; broad metaventral processes bifurcate at apex; protibia with small apical spine; mesotrochanter with tiny ventral spine.
Female. Unknown. Distribution. China: Jiangxi ( Figure 11A). Etymology. The new specific epithet refers to the long and bifurcate metaventral processes. Comparative notes. The new species belongs to the L. cardialis-group based on the strongly modified male antennomere IX. Linan divaricatus is most similar to L. huapingensis and L. geneolatus sp. n. (described below) in sharing both the angulate anterolateral corner of male antennomere IX, and median lobe of aedeagus strongly constricted at middle of the apex. From both latter species the new species differs by the relatively much broader antennomere IX, much broader metaventral processes bifurcate at the apex, and simple metatrochanter. In L. geneolatus sp. n., the male antennomere X is also strongly excavate at basal half. Diagnosis of male. Length 3.06 mm; postgenae broadly expanded laterally; antennomeres IX-X strongly modified, IX strongly projecting at anterolateral corner, X broadly concave at basal half; metaventral processes short; metatrochanter with short, blunt ventral projection.
Description. Male ( Figure 4B). Length 3.06 mm. Head slightly longer than wide, HL 0.69 mm, HW 0.66 mm; postgenae expanded laterally; eyes prominent, each composed of about 22 facets. Antenna with scape about 3.8 times as long as wide, antennomeres II-IV and VIII similar, each about as long as wide, V-VII each slightly longer than wide, antennomere IX ( Figure 6A) broad, strongly projecting at anterolateral corner, antennomere X transverse, broadly concave at basal half. Pronotum ( Figure 6B)  about as long as wide, PL 0.60 mm, PW 0.59 mm. Elytra much wider than long, EL 0.69 mm, EW 0.98 mm. Metaventral processes ( Figure 6C) short, narrowing at apex in lateral view. Protrochanter and profemur ( Figure 6D), and mesotrochanter and mesofemur ( Figure 6E) simple; metatrochanter ( Figure 6F) with short, blunt ventral projection. Abdomen slightly wider than elytra, AL 0.99 mm, AW 1.06 mm; tergite IV about twice as long as tergite V; sternite IX as in Figure 6G. Length of aedeagus ( Figure  6H-J) 0.44 mm; median lobe nearly symmetric, strongly constricted at middle of apex.

Etymology.
The new specific epithet refers to the strongly expanded postocular margins.
Comparative notes. The new species is placed as a member of the L. cardialis-group based on the strongly modified antennomere IX in the male, and is most similar to L. huapingensis in the shape of antennomere IX and spinose metatrochanter in the male. These two species can be separated by antennomere X being strongly excavate at the basal half, and the short metaventral processes in males of the new species, while in L. huapingensis the antennomere X lacks an excavation, and the metaventral processes are much longer and thinner. Otherwise, Linan geneolatus is the only member of the genus that exhibits broadened postgenae, which makes it readily separable from all other congeners. Diagnosis of male. Length 3.25-3.35 mm; antennomere IX-X strongly modified, IX strongly expanded and bent at lateral margin, with distinct process at anteromesal corner; broad metaventral processes expanded at apex in lateral view; metacoxa with roundly triangular ventral projection.
Comparative notes. The new species is placed as a member of the L. cardialisgroup based on the modified male antennomere IX, and most similar to L. hain- anicus Hlaváč in shape of male antennomere IX. They can be readily separated by the much broader metaventral processes, lack of a large apical projection of the protibia, complete symmetric aedeagal median lobe, and different structures of the endophallus of the new species. The broad metaventral processes, projecting metacoxae, and high symmetry of the aedeagal median lobe are shared by L. uenoi Yin & Nomura from Guangxi. They differ mainly by the modified antennomeres VII-VIII of L. uenoi, a quite distinct feature for a member of Linan. Diagnosis of male. Length 2.75-2.77 mm; antennomeres IX-XI elongate, lacking modification; long metaventral processes narrowed apically; protibia with acute apical spine; metacoxa with large, apically narrowing and blunt ventral projection.