Kekveus jason gen. et sp. nov. from Cretaceous Burmese amber, the first extinct genus and the oldest named featherwing beetle (Coleoptera: Ptiliidae: Discheramocephalini)

Abstract Featherwing beetles, or Ptiliidae (Coleoptera: Staphylinoidea), are characterized by their minute sized-body and peculiar hind wing structures, and include the smallest free-living insects. A half millimeter-long, unsexed adult featherwing beetle from Upper Cretaceous Burmese amber is here described as Kekveus jason gen. et sp. nov. Our observation recovered fine morphological details, such as the fringes of hind wings and pronotal grooves, from the Mesozoic Ptiliidae for the first time. Among Ptiliidae, this is the first nominal extinct genus, the first named representative from Burmese amber, the oldest named fossil, and the first named fossil from the Mesozoic Era. The new taxon is phylogenetically nested deep inside the crown group of Ptiliidae and is hypothesized to belong to the extant tribe Discheramocephalini, as either a member of, a sister to, the clade formed by the genera Skidmorella and Discheramocephalus . Our finding indicates the miniaturization in Ptiliidae can be reliably traced back to at least mid-Cretaceous.