Extinct and extant rove beetles meet in the matrix: Early Cretaceous fossils shed light on the evolution of a hyperdiverse insect lineage (Coleoptera: Staphylinidae: Staphylininae).

Description of the Early Cretaceous (Yixian Formation, China) fauna of Staphylininae and Paederinae rove beetles, and a rigorous (maximum parsimony, maximum likelihood and Bayesian inference) phylogenetic analysis of both extinct and extant taxa resulted in the following discoveries: a stem lineage sister to Staphylininae + Paederinae; a new tribe for Staphylininae, Thayeralinini trib. n.; several extinct species of the extant tribe Arrowinini; extinct basal lineages of the extant tribe Staphylinini; two stem genera of the "Xantholinine-lineage" (Staphylininae); and recovery of Mesostaphylinus in Paederinae with several new species. It is demonstrated that by the Early Cretaceous, Paederinae and Staphylininae were already diversified into groups, some of which now represent extant tribes but not the branches dominating in the modern biota. While the study of the Early Cretaceous rove beetle fauna pushes the estimated divergence time between Paederinae and Staphylininae down into the Jurassic, it also suggests that presently hyperdiverse groups of Staphylininae originated some time later than the Early Cretaceous. In addition to one new tribe, five new genera (Paleothius, Cretoprosopus, Thayeralinus, Paleowinus and Durothorax) and 17 new species are described in Staphylininae, and three new species of Mesostaphylinus are described in Paederinae. Mesostaphylinus fraternus (incertae sedis) is moved to the genus Thayeralinus (Staphylininae).