Platystethus bucerus, Lü, Liang & Zhou, Hong-Zhang, 2015

Lü, Liang & Zhou, Hong-Zhang, 2015, Review of the Genus Platystethus Mannerheim (Coleoptera: Staphylinidae: Oxytelinae) in China, Zootaxa 3915 (2), pp. 151-205 : 159-162

2. Platystethus bucerus sp. nov.

( Figs. 3 & 4 )

Type material examined. Holotype: CHINA: Tibet, Nyingchi, Sehgyla Mountain Pass, 29.61033ºN 94.65156ºE, 4565 m, under rocks, 2006. IX.1 day, Liang H.B. & Bai M. legg. (IZ-CAS). Paratypes: 8♂♂, 2♀♀, same data as holotype (IZ-CAS). Sichuan: 1♂, Wolong, Balangshan [Mt. Balang], 4500 m, waterside, 2003. VIII.25, H.-Z. Zhou & C.- Y. Zhao leg. (IZ-CAS).

Description. Body black; mandibles, maxillary palpi, elytra, legs reddish. Length [average]: ♂, 4.4 mm; ♀, 5 mm.

Male. Head ( Figs. 3 A; 4A) broadest at temples, some cases at eyes. Disc coriaceous, nearly glabrous, with punctures fine but dense. Clypeus transverse, with anterior margin slightly emarginate, furnished with short sharp process, bordered with membrane at each side. Epistomal suture with middle portion absent, lateral portions short and obscure and posteromedially directed. Supra-antennal ridges obviously elevated and anteriorly horned. Vertex depressed in anterior part, convex at each side of mid-longitudinal suture; mid-longitudinal suture short and deep, posteriorly reaching occipital suture. Eyes slightly convex, shorter than temples, with fine facets; orbital sulcus fine. Temple dilated laterally. Occipital suture deep and arciform. Mandible ( Fig. 4 C) long, stout, and dull and incurved at apex; bearing 3 teeth on inner edge: 2 large with 1 tiny in between; with tiny spur situated in fovea at middle of dorsal surface.

Pronotum ( Figs. 3 A; 4A) as wide as head, widest at anterior 1/3, with mid-longitudinal sulcus throughout, with punctures sparser than in head, micro-striate between punctures; anterior margin bi-emarginate, anterior lateral angles produced, no posterior angles; lateral and posterior margins integrated and evenly rounded, without crenulation. Scutellar impression heart-shaped, anterior margins crescent. Elytra with posterior margin truncate, elytral suture dehiscent.

Abdomen coriaceous. Sternite VII ( Figs. 3 C; 4E) with posterior margin slightly protruding in middle. Sternite VIII ( Figs. 3 D; 4F) tri-partitioned by 2 curved narrow sutures, middle part with posterior margin rounded but protruding in middle and with mid-longitudinal internal ridge throughout, lateral parts completely separated by middle part, each at mesial side with long process (longer than that in P. arenarius ) situated with short seta at apex; basal ridge interrupted in middle, sub-basal ridge with middle portion absent.

Aedeagus ( Figs. 3 G–I; 4I –L) with median lobe bottle-like, inflated at base; apical orifice large and fissured to middle of ventral surface, and broadened and embedded with sharp triangular sclerite there, edges of ventral fissure dully protruding, incrassated, and sparsely pubescent near apex; internal sac membranous. Paramere arm-like, basal arm with furrow on ventral surface; apical arm furnished with small seta at apex, stout seta at slight protrusion near apex, and with pits scattered, dorsomesial side with sharp triangular process directed reversely.

Female. Head ( Figs. 3 B; 4B) smaller, narrower than pronotum; clypeus longer, truncate to slightly curved in anterior margin; epistomal suture with lateral portion longer and obvious; supra-antennal ridges horned but shorter than in male; vertex slightly convex at side of mid-longitudinal suture; eyes convex, nearly equal to temples in length, temples not dilated. Mandibles ( Fig. 4 D) shorter and sharper than in male. Pronotal anterior margin with biemargination weak. Abdominal sternite VII with posterior margin straight. Sternite VIII ( Figs. 3 E; 4G) not partitioned, without processes, with posterior margin broadly rounded and a little protruding in middle.

Spermatheca ( Figs. 3 F; 4H) clavate, with basal part inflated into globoid and apical part slender (longer than that of P. arenarius ).

Distribution. Sichuan, Xizang [=Tibet].

Etymology. The specific epithet is derived from the Latin adjective “ bucerus ”, which means “ox-horned”, to indicate the horned supra-antennal ridge of the new species and that is easily associated with the horn of an ox.

Remarks. P. bucerus sp. nov. must be allied to P. arenarius and P. erlangshanus , and they are all distributed in Sichuan and Xizang. But this new species can be separated by the horned supra-antennal ridges of both male and female individuals. P. bucerus sp. nov. is darker than the other two in elytral color, and is prone to be found at higher elevations.

Figures

FIGURE 3. Platystethus bucerus sp. nov. I: A, head and pronotum ♂ (dorsal view); B, head and pronotum ♀ (dorsal view); C, sternite VII ♂; D, sternite VIII ♂; E, sternite VIII ♀; F, spermatheca; G, aedeagus (ventral view); H, median lobe of aedeagus (lateral view); I, right paramere (in situ) of aedeagus (lateral view). Scales: A, B = 0.5 mm; F = 0.05 mm; rest, 0.2 mm.

FIGURE 4. Platystethus bucerus sp. nov. II: A, head and pronotum ♂ (dorsal view); B, head and pronotum ♀ (dorsal view); C, right mandible ♂; D, right mandible ♀; E, sternite VII ♂; F, sternite VIII ♂; G, sternite VIII ♀; H, spermatheca; I, aedeagus (ventral view); J, aedeagus (dorsal view); K, median lobe of aedeagus (lateral view); L, right paramere (in situ) of aedeagus (lateral view). Scales: A, B = 1 mm; H = 0.05 mm; rest, 0.3 mm.