New Cretaceous empidoids and the Mesozoic dance fly revolution (Diptera: Empidoidea)

Dance flies and relatives (Empidoidea) are a diverse and ecologically important group of Diptera in nearly all modern terres-trial ecosystems. Their fossil record, despite being scattered, attests to a long evolutionary history dating back to the early Meso-zoic. Here, we describe seven new species of Empidoidea from Cretaceous Kachin amber inclusions, assigning them to the newgenus Electrochoreutes gen.n. (type species: Electrochoreutes trisetigerus sp.n.) based on unique apomorphies among known Dip-tera. Like many extant dance flies, the males of Electrochoreutes are characterized by species-specific sexually dimorphic traits,which are likely to have played a role in courtship. The fine anatomy of the fossils was investigated through high-resolution X-ray phase-contrast microtomography to reconstruct their phylogenetic affinities within the empidoid clade, using cladistic reason-ing. Morphology-based phylogenetic analyses including a selection of all extant family- and subfamily-ranked empidoid cladesalong with representatives of all extinct Mesozoic genera, were performed using a broad range of analytical methods (maximumparsimony, maximum-likelihood and Bayesian inference). These analyses converged in reconstructing Electrochoreutes as a stem-group representative of the Dolichopodidae, suggesting that complex mating rituals evolved in this lineage during the Cretaceous.