Rove beetles of the genus Piestus Gravenhorst, 1806 are commonly captured under the bark of or inside decaying logs from Neotropical forests. Piestus belongs to the subfamily Piestinae, historically an ill-defined dumping-ground for Staphylinidae defined by plesiomorphic characters, but which has gradually been restricted in concept and currently includes only six additional extant genera worldwide. Piestinae in this restricted sense has been considered a probably monophyletic subfamily, but its status and phylogenetic position, as a possible sister-group of Osoriinae within the recently proposed Oxyteline group of staphylinid subfamilies, are uncertain and need confirmation. The main aim of the present study was to provide a morphological cladistic analysis and complete taxonomic revision of Piestus, which, as the type and most speciose genus of Piestinae, is critical for future phylogenetic studies involving the subfamily. In our study, the monophyly of Piestus is established and phylogenetic relationships among its species are proposed based on 70 adult morphological characters. Piestus is supported by 11 synapomorphies and high branch support. All species of Piestus are revised and the genus is redefined. The genus contains 43 species, including 13 species described here for the first time. The previously proposed subgenera Antropiestus Bernhauer, 1917, Eccoptopiestus Scheerpeltz, 1952, Elytropiestus Scheerpeltz, 1952, Lissopiestus Scheerpeltz, 1952, Piestus s. str., Trachypiestus Scheerpeltz, 1952 and Zirophorus Dalman, 1821 have not been confirmed, as they were found to be poly- or paraphyletic, or are here removed from Piestus, and therefore subgenera are not used. The main taxonomic changes are as follows. Lissopiestus, syn. nov. is proposed as new synonym of Eleusis Laporte, 1835 and its species, E. interrupta (Erichson, 1840), comb. rest., is transferred again to that genus. Antropiestus, syn. nov. and Eccoptopiestus, syn. nov. are proposed as new synonyms of Hypotelus Erichson, 1839 and their species, H. laevis (Solsky, 1872), comb. nov. and H. andinus (Bernhauer, 1917), comb. nov., are transferred to Hypotelus. Fourteen new synonymies are proposed (valid species listed first): P. lacordairei Laporte, 1835 = Z. furcatus Sharp, 1887, syn. nov.; P. capricornis Laporte, 1835 = P. frontalis Sharp, 1876, syn. nov.; P. pennicornis Fauvel, 1864 = P. plagiatus Fauvel, 1864, syn. nov.; P. rectus Sharp, 1876, syn. nov.; P. pygialis Fauvel, 1902, syn. nov.; P. surinamensis Bernhauer, 1928, syn. nov.; P. minutus Erichson, 1840 = P. nigrator Fauvel, 1902, syn. nov.; P. sulcatus Gravenhorst, 1806 = P. sanctaecatharinae Bernhauer, 1906, syn. nov.; P. condei Wendeler, 1955, syn. nov.; P. gounellei Fauvel, 1902 = P. wasmanni Fauvel, 1902, syn. nov.; P. mexicanus Laporte, 1835 = P. alternans Sharp, 1887, syn. nov.; P. aper Sharp, 1876 = P. schadei Scheerpeltz, 1952, syn. nov.; P. angularis Fauvel, 1864 = P. crassicornis Sharp, 1887, syn. nov.; H. andinus (Bernhauer, 1917) = P. strigipennis Bernhauer, 1921, syn. nov. One species is revalidated: P. fronticornis (Dalman, 1821), stat. rev., and one synonym is restored: P. penicillatus (Dalman, 1821) = P. erythropus Erichson, 1840, syn. rest. Neotypes are designated for P. lacordairei Laporte, 1835 and Oxytelus bicornis Olivier, 1811, and lectotypes are designated for P. puncticollis Fauvel, 1902, P. capricornis variety muticus Fauvel, 1902, P. zischkai Scheerpeltz, 1951, P. pennicornis Fauvel, 1864, P. plagiatus Fauvel, 1864, P. pygmaeus Laporte, 1835, P. niger Fauvel 1864, P. minutus Erichson, 1840, P. nigratror Fauvel, 1902, P. sulcatus Gravenhorst, 1806, P. sanctaecatharinae Bernhauer, 1906, P. sulcipennis Scheerpeltz, 1952, P. aper Sharp, 1876, P. schadei Scheerpeltz, 1952 and P. andinus Bernhauer, 1917.
Taxonomic revision of Amorimia W.R. Anderson (Malpighiaceae)
