Evolution of Mastigitae: Mesozoic and Cenozoic fossils crucial for reclassification of extant tribes (Coleoptera: Staphylinidae: Scydmaeninae)

Abstract

Mastigitae is a supertribe of ant-like stone beetles (Scydmaeninae) that includes over 40% extinct genera, and whose evolutionary history is documented from the Upper Cretaceous through to today. Based on the results of phylogenetic analyses combining the most extensive taxon sampling to date, we reclassify Mastigitae into six monophyletic units: Leptomastacini, Clidicini sensu nov., Papusini trib. nov., Leptochromini trib. nov., †Baltostigini trib. nov. and Mastigini sensu nov. †Cretoleptochromus is placed as a junior synonym of Clidicus, and †Cascomastigus as a junior synonym of †Clidicostigus. Euroleptochromus setifer sp. nov. and Baltostigus striatipennis sp. nov. are both described from Upper Eocene Baltic amber. We postulate that Mastigitae have undergone differentiation into major lineages before the Cenomanian and that the Eurasian part of Laurasia was their ancestral distribution area. The reconstructed ancestor of Mastigitae was similar to the extant Scydmaenini, but with broadly separated antennal insertions and deep elytral striae. Four independent wing losses were inferred in Mastigitae. We present the first complete μCT reconstruction of the aedeagus in a fossilized scydmaenine, crucial for understanding the more than 99 million year long evolution of one of the most bizarre, asymmetrical aedeagi in the Coleoptera.