A new genus and species of Miocene Sepsidae (Diptera), the first definitive fossil of the family

The first sespid known in Miocene amber from the Dominican Republic is described based on a unique male specimen, Chaetosepsis caribea, n. gen., n. sp. Four compression fossil species in Cenozoic shales attributed to Sepsidae were assessed: Themira saxifica Melander, in Late Eocene shale from Florissant, Colorado, is Diptera family incertae sedis; Sepsis atra Statz, S. ignobilis Statz, and S. bicolorata Statz, all from Oligocene shales of Hennef, Germany, are in Empidoidea. Protorygma electricum Hennig, in Late Eocene Baltic amber, is a stem group to Sepsidae or to Sepsidae + Ropalomeridae. Chaetosepsis thus appears to be the first definitive fossil of the family. The new genus has numerous, bristlelike setae, an osmeterium on the hind tibia, and sternite four with large lateral arms each bearing a thick brush of long setae, among other distinctive features. Phylogenetic position lies among the extant basal genera Zuskamira Pont, Susanomira Pont, and Themira Robineau-Desvoidy, which is biogeographically unusual given the lowland tropical origin of Dominican amber and the Holarctic distribution of the closest extant relatives of Chaetosepsis.