Contribution to the knowledge of the tribe Mastigerina (Coleoptera: Staphylinidae: Pselaphinae, Clavigeritae), with a description of a new genus from Borneo Hlaváč, Peter Zootaxa 2011 3070 51 59 4NGZF [151,443,332,358] Insecta Staphylinidae Pseudacerus GBIF Animalia Coleoptera 3 54 Arthropoda species sabahensis sp. nov.    Typematerial(533).  Holotype: MALAYSIA:3, “Sabah, Ulu Segama Forest Res., 8.IV.05, FIT, plot 5, 10 km from Danum Valley FC [ N05°02.68‘ E117°45.55‘], leg. Slade & Villanueva / Primary rain forest / [red label] HOLOTYPE  Pseudacerus sabahensisP. Hlaváčdet., 2009” ( OXUM).  Paratypes: MALAYSIA:3, same data as holotype( OXUM); 333, “Borneo: Sabah, Lahat Datu, Ulu Segama Forst. Res., Malua 2 Logging area, 250 m, 05°05.731’N 117°37.606’E, III.2005, E. Slade & J. Villanueva lgt. / FIT #2 Forest High intensity dipterocarp frst Yayasan Sabah Logging Concession, OUMNH-2005-062” ( OXUM33, CPH233). All paratypesbear the following red label: “ PARATYPE  Pseudacerus sabahensisP. H laváč det., 2009”.   Description.Body ( Fig. 2) shiny reddish brown, antennae and legs yellowish brown, length 1.42–1.51 mm, maximum width of elytra 0.86–0.88 mm. Head widest at base, about 1.2–1.3 times as wide as long, space between eyes about twice as wide as dorsal width of one eye, with microreticulation at base between eyes, with few punctures at sides, vertex and rostrum smooth, antennomere III twice as long as wide. Pronotum slightly more than twice as wide as long, finely shagreened and with few irregularly placed punctures, surface with sparse long setae, lateral margin with six long setae. Metaventrite with large punctures only on metaventral process, punctures evanescent toward process base, sides of metaventrite smooth with sparse setation. Elytra about twice as long as pronotum, in anterior half of disc with regular and sparse isodiametric structures, posteriorly evenly covered by very long setae, longer than diameter of punctures of isodiametric structure. Posterior angle less carinate, but clearly protuberant. Abdomen. Composite tergite (IV–VI) with deep median cavity delimited by median arched border close to apex of composite tergite. Paratergites of composite tergite well-developed, widest in basal part, bearing five trichomes, two large triangular trichomes and three long and narrow, macroseta-like trichomes, triangular trichomes longer than maximal width of paratergite. Tergites VII and VIII visible dorsally. First visible sternite with large median carina and deep lateral depressions. Aedeagus as in Figs. 8–9. Sexual dimorphism. In male legs ( Fig. 5) with mesofemora bearing relatively straight obtuse spines, mesotibiae with triangular, obtuse, ill-defined tooth located in basal part before middle of tibiae, apex of mesotibia with spur. Female unknown.   Remarks.  Pseudacerus sabahensisdiffers from its congeneric species  P. furcatusby the much longer setation on the whole surface of the elytra, by the larger triangular basal trichome that is longer than the maximum width of the paratergite, and by the different structure of the mesofemora, mesotibiae, metaventrite and first visible sternite.   Distribution.Known only from the typelocality, Danum Valley Forest Center, Ulu Segama Forest Reserve, Borneo (Sabah).   Etymology.The name of the new species refers to the name of the state, Sabah, where the new species was collected.