Description of Euroleptochromus gen.n. (Coleoptera, Staphylinidae, Scydmaeninae) from Baltic amber, with discussion of biogeography and mouthpart evolution within Clidicini

A new extinct species of the ant-like stone beetle supertribe Mastigitae, Euroleptochromus sabathigen. & sp.n. is described from Eocene Baltic amber. A phylogenetic analysis of Clidicini, with representatives of Leptomastacini and Mastigini as out-group taxa, provided strong support for a sister-group relationship between the Neotropical Leptochromus and the new genus. The monophyly of Clidicini is questioned because of an alternative placement of Nearctic Papusus as a sister taxon to Leptomastacini + [Clidicus + (Palaeoleptochromus + (Euroleptochromus + Leptochromus))]. A dispersal-vicariance analysis provided three alternative scenarios for the evolution of Mastigitae; with Laurasia as the ancestral area of the supertribe, major branching events occurring within either Eurasia or Laurentia and two trans-Beringia dispersals in Late Cretaceous and Eocene. Euroleptochromus, Palaeoleptochromus and Leptochromus share highly derived structures on postgenae and maxillary palps, probably as part of a specialised feeding or prey capture mechanism. The formation of these modifications in Clidicini is demonstrated to involve a process (traced back to the Campanian, 79 Ma) of elongation and narrowing of maxillary palps and forming a cuticular setal projection from a broadened insertion site of sensory setae.