Two new genera of Lathrobiina from the East Palaearctic region (Coleoptera: Staphylinidae: Paederinae)

Two genera of Lathrobiina are described, illustrated, and distinguished from Lathrobium Gravenhorst, 1802 and allied genera: Elytrobium gen. n. (type species: Lathrobium monilicorne Sharp, 1889) and Sinlathrobium gen. n. (type species: Lathrobium lobrathiforme Assing, 2012). Elytrobium is distributed in the southeast of the East Palaearctic region and includes six species: E. monilicorne (Sharp, 1889), comb. n. (Japan); E. gongganum sp. n. (China: Gongga Shan); E. qinlinganum sp. n. (China: Qinling Shan); E. seminitidum sp. n. (China: Shaanxi); E. scindens sp. n. (China: Daba Shan); E. alesianum sp. n. (Taiwan). Sinlathrobium comprises four species from China: S. lobrathiforme (Assing, 2012), comb. n. (Yunnan); S. lobrathioides (Assing, 2012), comb. n. (transferred from Lathrobium) (Chongqing); S. densepunctatum sp. n. (Sichuan); S. iniquum sp. n. (Yunnan). Keys to the species of both genera are provided, and their distributions are mapped. Although all the species of both genera appear to be fully winged, four of the six Elytrobium and all the Sinlathrobium species have been recorded from only a single locality each. Three Elytrobium and three Sinlathrobium species are currently represented only by their respective holotypes.


Introduction
A comprehensive phylogenetic study of the Lathrobiina has never been attempted. Traditionally, the genera have been distinguished based on morphological characters such as the shape of the head, the presence/absence of a supramarginal line of the elytra, the width of the posterior constriction of the head, the length of metatarsomere I, the punctation of the elytra, the presence/absence of long setae on the tibiae, the presence/absence of a median carina on the abdominal sternite III, and the position of the aedeagus in the abdomen (Coiffait 1982). However, at least some of these characters may be subject to intrageneric variation. For instance, the supramarginal line of the elytra that has been regarded has an important character separating Lobrathium from Lathrobium was found to be absent in some micropterous Lobrathium species from Taiwan (Assing 2010a).
While some genera such as Achenium, Pseudobium, Throbalium, and Tetartopeus are well-defined and readily identified, others are weakly delimited due to the absence of clear-cut synapomorphies separating them. This is particularly true of Lobrathium, Platydomene, and Domene, which are usually distinguished based on -occasionally overlapping -characters related to their habitus.
In the course of recent revisions of several lathrobiine genera (Achenium, Lathrobium, Lobrathium, Pseudolathra, Pseudobium, Tetartopeus) from the Palaearctic and Oriental regions (e.g. Assing 2009Assing , 2010aAssing , b, 2011Assing , b, 2013a in press a), nine species represented by only few specimens, most of them found in material from the collections of Aleš Smetana (Ottawa) and Michael Schülke (Berlin), were discovered that did not seem to fit into any of the known genera of Lathrobiina. Two of them were tentatively described in the genus Lathrobium . A tenth species was recently seen while revising type material of some Lathrobium species described by Sharp (1889) from Japan (Assing in press a). Based on a comparative study of morphological characters, they are hypothesized to represent two undescribed genera.

Material and methods
The material treated in this study is deposited in the following public institutions and private collections: The morphological studies were conducted using a Stemi SV 11 microscope (Zeiss Germany) and a Jenalab compound microscope (Carl Zeiss Jena). A digital camera (Nikon Coolpix 995) was used for the photographs. The maps were created using MapCreator 2.0 (primap) software.
Body length was measured from the anterior margin of the mandibles (in resting position) to the abdominal apex, the length of the forebody from the anterior margin of the mandibles to the posterior margin of the elytra, head length from the anterior margin of the frons to the posterior mar gin of the head, elytral length at the suture from the apex of the scutellum to the posterior margin of the elytra (at the suture), and the length of the aedeagus from the apex of the ventral process to the base of the aedeagal capsule. The "parameral" side (i.e., the side where the sperm duct enters) is referred to as the ventral, the opposite side as the dorsal aspect.
Type species: Lathrobium monilicorne Sharp, 1889 Etymology: The name (gender: neuter) is composed of the Greek word elytron and the ending of the generic name Lathrobium. It alludes to the long elytra combined with a habitus somewhat resembling species of Lathrobium.
Head (e.g., Figs 2,8,15,23) rather small in relation to body and slender, oblong, mostly broadest across eyes, and more or less distinctly tapering behind eyes; posterior angles rounded, noticeable or obsolete; neck approximately half the width of head; punctation on dorsal surface distinct; interstices with microreticulation; ventral aspect (Fig. 32) strongly, rugosely sculptured, matt, and with shallow punctures; gular sutures broadly separated; genal carinae absent. Eyes convex, composed of numerous fine ommatidia, and at least as long as half distance from posterior margin of eye to neck. Antenna (Figs 16,24,47) moderately slender; antennomeres V-X about as long as broad or weakly oblong. Maxillary palpomere III of variable morphology, slender to conspicuously dilated, 2.0-3.5 times as long as broad. Labial palpus ( Fig. 42) short, with weakly oblong palpomeres I and II, and with relatively short palpomere III. Mandibles (Fig. 40) as in Lathrobium. Labrum ( Fig. 41) distinctly, but not very deeply bilobed.
Elytra (e.g., Figs 2,8,15,23) conspicuously long and broad in relation to pronotum; supramarginal line absent; punctation distinct, irregular or arranged in indistinct series. Hind wings fully developed. Ventral aspect of meso-and metathorax as in Lathrobium. Protarsomeres I-IV distinctly dilated in both sexes. Metatarsomere I approximately as long as II.
Abdomen narrower than elytra; punctation dense and distinct on anterior tergites, gradually becoming finer and sparser towards the abdominal apex; tergite VII with palisade fringe; tergite VIII without sexual dimorphism and with truncate posterior margin; sternite III with long and pronounced median keel extending over the full length of sternite; sternites III-VI without sexual dimorphism; tergites IX and X without sexual dimorphism, tergite IX long, slender, and undivided in the middle, postero-lateral processes apically with spine-like process (Fig. 39); tergite X small, much shorter than antero-median portion of tergite IX (Fig. 39).

Comparative notes:
Among the Lathrobiina, the new genus is readily identified by external characters alone, particularly the small, oblong, distinctly microsculptured, and posteriorly more or less distinctly tapering head combined with dark coloration, and long elytra. In addition, it is characterized by weakly modified male sternites VII and VIII, as well as by a distinctive shape of the aedeagus without sclerotized internal structures. Among the genera currently attributed to the Lathrobiina, Elytrobium has some resemblance only to Lathrobium and some genera treated as subgenera of Lathrobium until several decades ago, in particular Tetartopeus and Lobrathium. Aside from the characters pointed out above, Elytrobium differs from the latter by the absence of a supramarginal line of the elytra. Regarding its head shape, Elytrobium is most similar to Tetartopeus, from which it is distinguished by the broader neck (Tetartopeus: neck distinctly less than half the width of head), by the completely different secondary sexual characters in both sexes, and by the completely different morphology of the aedeagus (Tetartopeus: aedeagus symmetric, with long, slender, and apically acute ventral process, with distinctly larger and more sclerotized dorsal plate, and with dark internal structures). For illustrations of Tetartopeus see Assing (2009Assing ( , 2011. Using the key to paederine genera in Coiffait (1982), Elytrobium would key out together with Lathrobium, the most speciose of all genera of Lathrobiina. Based on revisionary studies of Lathrobium from both the West and the East Palaearctic region, it is concluded that Elytrobium represents a distinct lineage. Despite a slight resemblance with some macropterous Lathrobium species, Elytrobium differs morphologically in numerous and significant respects: head smaller and posteriorly usually tapering; ventral aspect of head conspicuously sculptured and with broadly separated gular sutures; labrum less deeply bilobed; labial palpus shorter and with less oblong palpomeres; pronotum of different shape (Lathrobium: pronotum with subparallel lateral margins or widest in anterior half); prosternal process longer and more acute; elytra conspicuously long; median keel of sternite III long; absence of a sexual dimorphism of tergites VIII-X; male sternites VII and VIII weakly modified; morphology of the aedeagus characteristic, internal structures absent. For illustrations of the labrum and the labium of the type species of Lathrobium, L. elongatum (Linnaeus, 1767), see Figs 43-44. In all the previously revised Lathrobium species the abdominal tergites IX and X are subject to a pronounced sexual dimorphism, most likely one of the main synapomorphies constituting the monophyly of the genus. In some species (groups) the aedeagus may be of highly derived morphology and lack internal structures. Likewise, some species (groups) have weakly modified male sternites VII and VIII. These conditions, however, undoubtedly represent secondary reductions and are not homologous to the condition in Elytrobium. Moreover, the male sternite IX in Lathrobium is mostly less acute anteriorly and more or less asymmetric, particularly so in species with an asymmetric aedeagus. Finally, the available data suggest that Elytrobium differs from Lathrobium also regarding its natural history. The vast majority of Lathrobium species inhabits the leaf litter layer of shrub and forest habitats or lives epigeically in unforested habitats such a lake shores, river banks, and arable land. However, the genus also includes numerous microphthalmous or anophthalmous, micropterous, and depigmented species with a hypogean habitat. For notes on Elytrobium see the following section.

Distribution and natural history:
The currently known distribution of Elytrobium is confined to the East Palaearctic: China, Taiwan, and Japan (Map 1). All the species of this genus have long elytra, fully developed hind wings, and are probably capable of flight. Nevertheless, they have been found only on very rare occasions. Except for E. monilicorne (two specimens), no more than one specimen was found in one locality, and three of the six species are represented only by singletons. These observations suggest that the Elytrobium species inhabit a special, cryptic habitat and are recorded only by coincidence. The specimens collected by Aleš Smetana (three species) were found in moss, leaf litter, and vegetation in moist to wet habitats, one was captured with a yellow pan trap.

Comment:
For details on the type material and on the lectotype designation see Assing (in press a).
Metatarsomere I approximately as long as II.
Abdomen narrower than elytra, segments III-VI of subequal width; punctation dense and distinct on anterior tergites, gradually becoming finer and sparser towards the abdominal apex; interstices with distinct microreticulation; posterior margin of tergite VII with palisade fringe.

Comparative notes:
Elytrobium monilicorne is the sole representative of the genus known from Japan. It is characterized by relatively large size, the conspicuously swollen maxillary palpomere III, and particularly by the shape of the aedeagus.

Distribution and natural history:
At present, the only confirmed record is from the Fujisan in Honshu, Japan (Map 1). The species was doubtfully reported also from Kamchatka (Naomi et al. 2000) and China (Jilin) (see Peng et al. 2012), but these records most likely refer to other species of Elytrobium and clearly require confirmation. Bionomic data are not available.

Etymology:
The specific epithet is an adjective derived from the name of the mountain where this species was discovered. tation coarse and dense, slightly sparser in median dorsal portion; interstices narrower than diameter of punctures (except in median dorsal portion), with distinct microreticulation, and subdued shine. Eyes moderately large and composed of numerous fine ommatidia, approximately 0.6 times as long as postocular region from posterior margin of eye to neck in dorsal view. Antenna 2.0 mm long; antennomeres IV-X weakly oblong. Maxillary palpomere III slender, approximately 3.5 times as long as broad.

Description
Pronotum ( Fig. 8 Abdomen distinctly narrower than elytra, segments III-VI of subequal width; punctation dense and distinct on anterior tergites, gradually becoming finer and sparser towards the abdominal apex; interstices with distinct microreticulation; posterior margin of tergite VII with palisade fringe. : sternite VII ( Fig. 9) moderately transverse and with weakly concave posterior margin, pubescence unmodified; sternite VIII ( Fig. 10) weakly oblong, posterior excision very shallow, but with noticeable angle in the middle, pubescence unmodified; sternite IX nearly symmetric and apically with long and acute process (Fig. 11); aedeagus 0.75 mm long, shaped as in Figs 12-13.

Comparative notes:
Elytrobium gongganum is distinguished from E. monilicorne by larger body size, the more slender antennae with oblong antennomeres IV-X, the much more slender maxillary palpomere III, the much finer and indistinctly seriate punctation of the elytra, the differently shaped male sternite VIII, as well as by the shape of the aedeagus.

Distribution and natural history:
The type locality is situated in the Gongga Shan, a mountain in western Sichuan (Map 1). The holotype was sifted from wet moss and grassy vegetation on large fallen trees in a swampy habitat around a shallow forest pond at an altitude of 2750 m (Smetana pers. comm.).

Etymology:
The specific epithet is an adjective derived from the name of the mountain range where this species was discovered.

Description:
Body length 6.8 mm; length of forebody 3.8 mm. Habitus as in Fig. 14. Coloration: body black; legs blackish-brown with reddish tarsi; antennae reddish-brown with slightly darker antennomere I.
Head ( Fig. 15) 1.05 times as long as broad, broadest across eyes, and distinctly tapering behind eyes; posterior angles broadly rounded, indistinct; punctation coarse and dense, slightly sparser in median dorsal portion; interstices narrower than diameter of punctures (except in median dorsal portion), with distinct microreticulation, and subdued shine. Eyes moderately large and composed of numerous fine ommatidia, approximately half as long as postocular region from posterior margin of eye to neck in dorsal view. Antenna (Fig. 16) 1.9 mm long; antennomeres IV-X barely noticeably oblong. Maxillary palpi with palpomere III moderately slender, approximately 3 times as long as broad.
Pronotum ( Fig. 15) rather slender, 1.2 times as long as broad and 1.08 times as broad as head, moderately convex in cross-section, broadest slightly behind middle; lateral margins nearly straight in dorsal view; punctation slightly coarser and sparser than that of head; interstices glossy, without microreticulation; impunctate median band narrow. Elytra (Fig. 15) very long and large, 1.18 times as long as pronotum; punctation dense, distinct, as coarse as that of pronotum, and indistinctly seriate; interstices without microreticulation, glossy. Hind wings fully developed. Protarsomeres I-IV strongly dilated. Metatarsomere I approximately as long as II.
Abdomen distinctly narrower than elytra, segments III-VI of subequal width; punctation dense and rather coarse on anterior tergites, gradually becoming finer and sparser towards the abdominal apex; interstices with distinct microreticulation; posterior margin of tergite VII with palisade fringe. : sternite VII (Fig. 17) moderately transverse and with very weakly concave posterior margin, pubescence unmodified; sternite VIII ( Fig. 18) distinctly oblong, nearly 1.2 times as long as broad, posterior excision shallow and with noticeable angle in the middle, pubescence unmodified; sternite IX ( Fig. 19) symmetric and apically acute; aedeagus larger than in other species of the genus, nearly 0.9 mm long, shaped as in Figs 20-21.

Comparative notes:
From the other species of similar size, E. gongganum and E. monilicorne, E. qinlinganum is distinguished by the more slender pronotum with straight lateral margins, the absence of microsculpture on the pronotum, the relatively longer and larger elytra, the distinctly oblong male sternite VIII, and the larger and differently shaped aedeagus. It additionally differs from E. gongganum by the different coloration of the antennae and the more glossy and much more coarsely punctate elytra, and from E. monilicorne by somewhat larger size, more slender maxillary palpomeres III, more slender antennae, and the angled posterior excision of the male sternite VIII.

Distribution and natural history:
The type locality is situated in the Qinling Shan in southern Shaanxi (Map 1). The holotype was collected in a stream valley with mixed deciduous forest and bamboo at an altitude of 1990 m.

Etymology:
The specific epithet (Latin, adjective: half-shiny) alludes to the glossy pronotum and elytra distinctly contrasting with the matt head.

Description:
Small species; body length 6.0 mm; length of forebody 3.0 mm. Habitus as in Fig. 22. Coloration: body black; legs reddish-brown with reddish tarsi and infuscate profemora; antennae reddish with slightly darker antennomere I.
Head (Fig. 23) 1.08 times as long as broad, broadest across eyes, and distinctly tapering behind eyes; posterior angles broadly rounded, indistinct; punctation coarse and dense, sparser in median dorsal portion; interstices nar-rower than diameter of punctures (except in median dorsal portion), with very distinct microreticulation, nearly matt. Eyes moderately large and composed of numerous fine ommatidia, approximately half as long as postocular region from posterior margin of eye to neck in dorsal view. Antenna (Fig. 24) 1.5 mm long; antennomeres IV-X approximately as long as broad. Maxillary palpi with palpomere III moderately dilated, approximately 2.5 times as long as broad.
Pronotum (Fig. 23) rather slender, 1.2 times as long as broad and 1.06 times as broad as head, distinctly convex in cross-section, broadest slightly behind middle; lateral margins weakly convex in dorsal view; punctation similar to that of head; interstices glossy, without microreticulation; impunctate median band confined to posterior half. Elytra (Fig. 23) moderately long, 1.03 times as long as pronotum; punctation dense, as coarse as that of pronotum, defined, and indistinctly seriate; interstices without microreticulation, glossy. Hind wings fully developed. Protarsomeres I-IV strongly dilated. Metatarsomere I approximately as long as II.
Abdomen narrower than elytra, segments III-VI of subequal width; punctation very dense and coarse on anterior tergites, gradually becoming finer and sparser towards the abdominal apex; interstices on tergites III-VI with indistinct microreticulation and glossy, on tergites VII-VIII with slightly more distinct microsculpture; posterior margin of tergite VII with palisade fringe.

Comparative notes:
Elytrobium seminitidum is characterized particularly by the glossy pronotum, elytra, and abdomen distinctly contrasting with the matt head, by the relatively short elytra, by the weakly transverse sternite VII, by the deeper posterior excision of the male sternite VIII, and by the shape of the aedeagus. It additionally differs from the preceding species by smaller body size.

Distribution and natural history:
The type locality is situated in the Jinggang Shan, Jiangxi province, southeastern China (Map 1), at an altitude of 1280 m.

Etymology:
The specific epithet is the present participle of the Latin verb scindere (to scratch) and refers to the distinctly hook-shaped apex of the ventral process of the aedeagus.
Head (Fig. 31)  Pronotum (Fig. 31) 1.20-1.23 times as long as broad and 1.12-1.13 times as broad as head, moderately convex in cross-section, broadest slightly behind middle; lateral margins weakly convex in dorsal view, nearly straight; punctation similar to that of head; interstices with distinct microreticulation; impunctate median band very narrow.
Metatarsomere I approximately as long as II.
Abdomen slightly narrower than elytra, segments III-VI of subequal width; punctation not very dense and moderately coarse on anterior tergites, gradually becoming finer and sparser towards the abdominal apex; interstices with shallow microreticulation; posterior margin of tergite VII with palisade fringe.
: sternite VIII (Fig. 38) 1.1 times as long as broad and with distinctly convex posterior margin; tergites IX-X as in Fig. 39.

Comparative notes:
Elytrobium scindens differs from the similarly small E. seminitidum particularly by the presence of microsculpture on the pronotum, the transversely impressed frons, the slightly shorter elytra with non-seriate punctation, the less coarse and less dense punctation of the abdomen, the much more transverse male sternite VII, the much shallower posterior excision of the male sternite VIII, and by the differently shaped aedeagus. From the other species (re-)described above it is readily distinguished by smaller body size alone.

Distribution and natural history:
The species is known from two localities in the Daba Shan, one at the border between Chongqing and southern Shaanxi, and one in western Hubei (Map 1). The holotype was sifted from moist to wet moss, fallen leaves and other debris around a small seepage in a secondary deciduous forest (Smetana pers. comm

Etymology:
It is with great pleasure that I dedicate this species to Aleš Smetana (Ottawa), one of the foremost staphylinidologists of all times, whose outstanding material from Taiwan has so significantly contributed to the knowledge of the staphylinid fauna of this island and who collected the majority of the type specimens studied in the present paper.
Head (Fig. 46) 1.12-1.15 times as long as broad, broadest across eyes or at posterior margin of eyes, tapering behind eyes; lateral margins smoothly curving towards neck in dorsal view; posterior angles indistinct; frons transversely impressed and with pronounced microsculpture; punctation coarse and dense, sparser in median dorsal portion; interstices narrower than diameter of punctures (except in median dorsal portion), with very distinct micro reticulation and subdued shine. Eyes mod-erately large and composed of numerous fine ommatidia, approximately half as long as postocular region from posterior margin of eye to neck in dorsal view. Antenna (Fig. 47) 1.5-1.6 mm long; antennomeres IV-X approximately as long as broad. Maxillary palpi with palpomere III distinctly dilated apicad, barely 2.5 times as long as broad.
Pronotum (Fig. 46) approximately 1.2 times as long as broad and 1.15-1.17 times as broad as head, moderately convex in cross-section, broadest slightly behind middle; lateral margins weakly convex in dorsal view, nearly straight; punctation similar to that of head; interstices with distinct microreticulation; impunctate median band very narrow and short, reaching neither anterior nor posterior margins.
: sternite VIII strongly oblong, approximately 1.3 times as long as broad and with distinctly convex posterior margin.

Comment:
The female from the Anmashan is only tentatively included in the type series. Its head is of slightly different shape (not tapering immediately behind eyes), the lateral margins of the pronotum are subparallel, the elytra are dark-brown, and the legs are paler than in the male specimens. These differences are interpreted as an expression of intraspecific variation until evidence suggesting otherwise becomes available. Nevertheless, except for the female sexual characters, the above description is exclusively based on the two males. The aedeagus appears to be subject to some intraspecific variation, too. In the paratype from the Takuanshan, it is somewhat smaller and the ventral process is apically more slender than in the holotype (Figs 51-55).

Comparative notes:
Both in external and in sexual characters, E. alesianum is most similar to E. scindens, from which it is distinguished by the different head shape, the longer elytra, the slightly shorter and more strongly dilated maxillary palpomere III, the less transverse male sternite VII, the more oblong male sternite VIII, the slightly smaller and differently shaped aedeagus, and the more strongly oblong female sternite VIII.

Distribution and natural history:
The species was discovered in three localities in Taiwan (Map 1). The holotype was sifted from debris, leaf litter, and moss along a stream in an old, probably original mixed broadleaved and coniferous forest, the male paratype was collected in a mostly coniferous forest by dipping moss and vegetation along two small ponds into water, and the female paratype was found in a yellow pan trap in a primary mixed forest (Smetana pers. comm.). The altitudes range from 1600 to 2225 m.

Etymology:
The name (gender: neuter) is composed of Sina, the ancient name for China, and the generic name Lathrobium. It alludes to the fact that the genus has been recorded only from China and to the hypothesized close phylogenetic affiliations with Lathrobium.

Description:
Species of moderately large size; body length 7.4-8.0 mm; length of forebody 3.8-4.4 mm. Habitus as in Figs 58, 72. Coloration characteristic: body black, elytra posteriorly with a defined orange spot and sometimes with the humeral angles diffusely reddish; legs and antennae of variable coloration.
Head (Figs 59, 73) of distinctive morphology, strongly transverse, at least approximately 1.15 times as broad as long, broadest across eyes; lateral margins behind eyes subparallel or weakly converging in dorsal view; posterior angles rounded, but noticeable; neck approximately half the width of head; dorsal surface uneven, with more or less distinct elevations and/or impressions; punctation areolate, coarse, and dense; interstices reduced to narrow ridges, with or without shallow microsculpture; vertex and/or antero-median dorsal portion usually with partly sparser and irregularly spaced punctures; anterior margin of frons impunctate; ventral aspect ( Fig. 66) with shallow microsculpture and with much sparser punctation, interstices on average broader than diameter of punctures; gular sutures rather broadly separated, area between sutures impunctate; genal carinae absent. Eyes strongly bulging, composed of numerous fine ommatidia, longer than postocular region, and 0.7-0.9 times as long as distance from posterior margin of eye to neck. Antenna (Figs 60, 74) moderately slender; antennomeres I-III distinctly oblong, IV weakly oblong, and V-X weakly oblong or about as broad as long. Maxillary palpus (Fig. 69) slender, palpomere III approximately three times as long as broad; palpomere IV needle-shaped and slender, approximately as long as width of palpomere III. Labium (Figs 70-71) with relatively slender palpi, with oblong palpomeres I and II, and with needle-shaped, rather long palpomere III. Mandibles (Fig. 67) as in Lathrobium. Labrum (Fig. 68)  to distinctly convex in dorsal view; punctation sparse to moderately dense, but less dense than that of head; interstices without microsculpture and glossy; prosternum with pronounced and apically acute process posteriorly.
Elytra (Figs 59, 73) moderately long, 0.90-0.97 times as long as pronotum; humeral angles pronounced; suture elevated and forming a rather distinct keel; supramarginal line absent; punctation moderately coarse, moderately sparse to dense, and not seriate; interstices without microsculpture. Hind wings presumably fully developed (examined only in S. iniquum). Mesoventrite approximately as long as broad, along middle with pronounced and anteriorly strongly projecting keel and with acute posterior process; metaventrite sparsely and finely punctate, with shallow microsculpture, and glossy. Protarsomeres I-IV distinctly dilated in both sexes. Metatarsomere I shorter than II.
Abdomen as broad as, or slightly narrower than elytra; segments III-VI of subequal width; punctation moderately coarse to fine and moderately sparse to dense; tergite VII with palisade fringe; tergite VIII without sexual dimorphism and with convex posterior margin; sternite III with pronounced, sharply elevated median keel not reaching posterior margin of sternite; tergites IX and X with sexual dimorphism, postero-lateral processes of tergite IX apically with spine-like process.
: tergite IX relatively short and broad, antero-median portion undivided in the middle, postero-lateral processes short; tergite X shorter than antero-median portion of tergite IX; sternites IV-VI with or without median impressions and modified pubescence; sternite VII ( : tergite IX divided along the middle and with relatively short postero-lateral processes (Assing 2012a: figure 328); tergite X longer than antero-median portion of tergite IX; sternite VIII with convex posterior margin (Assing 2012a: figure 327), posterior portion with short yellow setae, but without micropubescence (Fig. 80).

Comparative notes:
Among the Lathrobiina, Sinlathrobium is readily identified by external characters alone, particularly the strongly transverse head with dense and somewhat areolate punctation and an uneven dorsal surface, the large and strongly bulging eyes, and by the coloration of the elytra. The coloration resembles that of some species of Lobrathium and Tetartopeus. From the former, the new genus additionally differs by the absence of a supramarginal line of the elytra, the absence of short and stout black setae on the male sternites VII and VIII (Lobrathium: usually present at least on sternite VIII), the presence of a sexual dimorphism of tergites IX and X, and the different morphology of the aedeagus (Lobrathium: ventral process of different shape, more or less strongly separated from remainder of aedeagus). From Tetartopeus, it is additionally distinguished by the broader neck, the different punctation of the elytra, the less dense punctation and pubescence of the abdomen, and by the completely different sexual characters.
Among the genera currently attributed to the Lathrobiina, Sinlathrobium is most similar to Lathrobium in most characters, e.g., the morphology of the mouthparts, the broad neck, the absence of a supramarginal line of the elytra, the punctation of the pronotum, elytra, and the abdomen, the ventral aspect of the head, thorax, and abdomen, and the presence of a sexual dimorphism of tergites IX and X. In Lathrobium, however, the head is of different morphology (different shape, less transverse, without distinct elevations or impressions; in species with a distinctly transverse head, the latter is usually dilated posteriad), the eyes are much less convex, the mesoventrite is transverse, the pronotum is usually more oblong, the anterior margin of the male sternite VII usually has a convex median projection, the ventral process of the aedeagus is somewhat separated from the aedeagal capsule (at least at the apex) and usually more or less distinctly curved ventrad, the aedeagus usually has distinct internal structures (except for some species and species groups with highly derived aedeagi), and the female sternite VIII is of different chaetotaxy (posterior portion with micropubescence). Moreover, a female tergite IX with a divided antero-median portion is known only from few species groups in Lathrobium . Based on the conspicuously derived head morphology, the synapomorphically derived modifications of the male sternites III-VIII, the similar morphology of the aedeagus, and numerous other similarities, the monophyly of Sinlathrobium is beyond doubt. The problem is identifying synapomorphies constituting the morphology of Lathrobium, its hypothesized adelphotaxon. As can be expected with a megadiverse taxon, character diverstity is enormous in Lathrobium, particularly regarding the sexual characters. Regarding external morphology, however, Lathrobium is remarkably constant and always readily identified. Species with a faintly similar head morphology and coloration are unknown in this genus, nor do the sexual or other external characters suggest a closer relationship to any of the species groups of Lathrobium known from China or from other regions in the Palaearc-tic region. These observations suggest that Sinlathrobium is not nested within Lathrobium, but forms a separate lineage.
Like the species of Elytrobium, Sinlathrobium species seem to have a cryptic habitat. Three of the four species are currently represented only by their respective holotypes, and the fourth species has been recorded only from one locality.

Distribution and natural history:
The currently known distribution of the four species of Sinlathrobium is confined to China (Map 2). Despite the presumably fully developed hind wings, there is no evidence suggesting that any of the four species are widespread; each of them is known from only one locality. The species have been sifted from leaf litter and moss in mixed and old deciduous forests and in a creek valley with Salix, Rhododendron, and other deciduous bushes at altitudes of 1800-3050 m.

Comment:
This species is known only from the holotype, which was collected in the Jinfo Shan in the south of Chongqing province, close to the border with Guizhou (Map 2). For illustrations of the external and the male sexual characters see

Etymology:
The specific epithet (Latin, adjective) refers to the densely punctate abdomen.

Description:
Body length 7.7 mm; length of forebody 4.1 mm. Habitus as in Fig. 58. Coloration: body black, elytra with rather extensive orange spot in postero-lateral angles, this spot reaching posterior and lateral margins, but not suture, humeral angles diffusely and indistinctly dark-reddish; legs with the femora blackish, the tibiae brown, and the tarsi reddish; antennae dark-brown, with antennomere I blackish and the bases of II and III reddish.
Head (Fig. 59) 1.17 times as broad as long, broadest across eyes, tapering behind eyes; dorsal surface between eyes uneven, in the middle with densely punctate impression; punctation coarse, dense, and somewhat areolate; interstices reduced to narrow ridges, with distinct microreticulation and nearly matt. Eyes strongly bulging, approximately 0.8 times as long as postocular region from posterior margin of eye to neck in dorsal view. Antenna (Fig. 60) 2.3 mm long; antennomeres IV-VIII distinctly, IX-X weakly oblong.
Pronotum (Fig. 59) 1.13 times as long as broad and 0.93 times as broad as head, distinctly convex in crosssection, broadest slightly before middle; lateral margins convex in dorsal view; punctation coarse, very dense in anterior third, somewhat less dense posteriorly; interstices glossy, without microsculpture; impunctate midline narrow and confined to posterior two-thirds of pronotum.
Abdomen slightly narrower than elytra; tergites III-IV anteriorly with coarse punctures, remainder of tergites III-VI with very fine and dense punctation, tergites VII-VIII with distinctly sparser punctation; posterior margin of tergite VII with palisade fringe.
: sternites III-VI without median impressions; sternite VII (Fig. 61) strongly transverse, 2.0 times as broad as long, with distinct postero-median impression, this impression with sparse black setae, near posterior margin on either side of postero-median impression with distinct transverse cluster of numerous stout black setae; sternite VIII (Fig. 62) transverse and with postero-median impression, postero-median portion without setae, posterior excision shallow; aedeagus (Figs 64-65) 1.1 mm long and symmetric; ventral process short and broad in ventral view; dorsal plate weakly sclerotized, apical portion broad, basal portion short and narrow. : unknown.

Comparative notes:
Sinlathrobium densepunctatum is easily distinguished from its congeners by the convex lateral margins of the pronotum in dorsal view, shorter tibiae, the finer and sparser punctation of the elytra, darker legs, the conspicuously dense and fine punctation of the abdomen, the more strongly transverse male sternite VII with a posterior pair of pronounced transverse clusters of stout black setae, the shallower posterior excision of the male sternite VIII, and by the shorter and broader ventral process of the aedeagus in ventral view.

Distribution and natural history:
The type locality is situated approximately 8 km to the southeast of Luding in western Sichuan (Map 2), at an altitude of 3000 m. Additional data are not available.

Etymology:
The specific epithet (Latin, adjective: uneven) alludes to presence of impressions and elevations on the head and the elytra.

Description:
Body length 8.0 mm; length of forebody 4.4 mm. Habitus as in Fig. 72. Coloration: body black, elytra with rather extensive orange spot in postero-lateral angles, this spot reaching posterior and lateral margins, but not suture; legs with the femora blackish, the tibiae blackish-brown, and the tarsi reddish; antennae dark-brown.
Head (Fig. 73) 1.15 times as broad as long, broadest across eyes; lateral margins behind eyes very weakly converging, nearly parallel in dorsal view; dorsal surface uneven, vertex with smooth median elevation, between eyes with two impressions near dorsal margins of eyes, frons with three small impressions; punctation coarse, dense in lateral and posterior portions of dorsal surface; median dorsal portion and frons with impunctate or more sparsely punctate areas; interstices without microsculpture and glossy. Eyes strongly bulging, approximately 0.8 times as long as postocular region from posterior margin of eye to neck in dorsal view. Antenna (Fig. 74) 2.2 mm long; antennomeres IV-V weakly oblong, VI-X as broad as long.
Pronotum (Fig. 73) weakly oblong, 1.08 times as long as broad and 0.98 times as broad as head, distinctly convex in cross-section, broadest anteriorly; lateral margins convex in dorsal view; punctation coarse and moderately dense; interstices glossy, without microsculpture; impunctate midline confined to posterior third of pronotum.
Abdomen slightly narrower than elytra; punctation distinct and moderately dense, slightly sparser on tergites VII-VIII than on tergites III-VI; posterior margin of tergite VII with palisade fringe.
: sternites III-VI with shallow median impressions; sternite VII ( Fig. 75) strongly transverse, 1.8 times as broad as long, with distinct postero-median impression, this impression without setae in the middle and posteriorly; postero-lateral portions with unmodified and not particularly dense dark setae, posterior margin weakly concave; sternite VIII ( Fig. 76) transverse and with postero-median impression, postero-median portion without setae, posterior excision moderately deep; aedeagus (Figs 78-79) 1.4 mm long and symmetric; ventral process in the middle conspicuously sculptured, apically acute in ventral view; dorsal plate reduced, weakly sclerotized, lamellate, apical portion small, basal portion minute; internal sac with membranous structure.

Comparative notes:
Sinlathrobium iniquum differs from all its congeners by the short and broad pronotum, the glossy elevations on the head, the uneven surface of the elytra, the shape and