Sinlathrobium, Assing, 2013

Assing, Volker, 2013, Two new genera of Lathrobiina from the East Palaearctic region (Coleoptera: Staphylinidae: Paederinae), Beiträge Zur Entomologie = Contributions to Entomology 63 (2), pp. 219-239 : 232-234

Sinlathrobium gen. n.

Type species: Lathrobium lobrathiforme ASSING, 2012

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 ) deeply bilobed.

Pronotum ( Figs 59 , 73 ) rather short, 1.08-1.16 times as long as broad and 0.91-0.98 times as broad as head, widest anteriorly or in the middle; lateral margins straight 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 ( Figs 61 , 75 ) strongly transverse, with pronounced postero-median impression, with or without modified pubescence, anterior margin without convex median projection; sternite VIII ( Figs 62 , 76 ) transverse, posterior excision moderately deep and anteriorly rounded; sternite IX ( Figs 63 , 77 ) asymmetric and anteriorly truncate, of similar shape as in Lathrobium ; aedeagus ( Figs 64-65 , 78-79 ) symmetric, ventral process dorso-ventrally flattened, not separated from aedeagal capsule; dorsal plate weakly sclerotized, lamellate and subdivided into an apical and a basal portion; internal sac with or without a membranous tube; parameres absent.

: 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 (ASSING 2013) .

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.

Sinlathrobium lobrathiforme (ASSING, 2012) , comb. n. ( Figs 66-71 , 80 , Map 2 )

Comment:

This species is known only from one locality in the northern Gaoligong Shan, northwest Yunnan, close to the bor- der with Myanmar ( ASSING 2012a, 2013) ( Map 2 ). The mouthparts, the ventral aspect of the head, and the female sternite VIII are illustrated in Figs 66-71 , 80 . For illustrations of the external and the male sexual characters see ASSING (2012a).

Sinlathrobium lobrathioides (ASSING, 2012) , comb. n. ( Map 2 )

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 ASSING (2012a) .

Figures

Map 2: Distribution of Sinlathrobium gen. n. in China: S. lobrathiforme (ASSING) (triangle); S. iniquum sp. n. (diamond); E. densepunctatum sp. n. (star); S. lobrathioides (ASSING) (circle).

Figs 58-71:Sinlathrobium densepunctatumsp. n. (58-65) andS. lobrathiforme(ASSING) (66-71): habitus(58); forebody (59); antenna (60); male sternite VII (61); male sternite VIII (62); male sternite IX (63); aedeagus in lateral and in ventral view (64-65); median portion of ventral aspect of head (66); mandibles in ventral view (67); labrum (68); maxillary palpus (69); labium (70); ligula (71). Scale bars: 58-59: 1.0 mm; 60-65: 0.5 mm; 66-70: 0.2 mm; 71: 0.1 mm.

Figs 72-80: Sinlathrobium iniquum sp. n. (72-79) and S. lobrathiforme (ASSING) (80): habitus (72); forebody (73); antenna (74); male sternite VII (75); male sternite VIII (76); male sternite IX (77); aedeagus in lateral and in ventral view (78-79); postero-median portion of female sternite VIII (80). Scale bars: 72-73: 1.0 mm; 74-79: 0.5 mm; 80: 0.1 mm.