Abstract: Evanioidea, as a poorly known group of Hymenoptera, exhibited remarkable species diversity during the Cretaceous, especially within the basal fossil family †Praeaulacidae. Here, we describe a new genus and species, †Coronaulacus cancan gen. et sp. nov., from Cretaceous Kachin amber. Based on its unique morphological characteristics and phylogenetic analysis, we place the new genus into †Praeaulacidae. This new genus is significantly distinct from other genera of the family: it is characterized by a ring of tubercles around the median ocellus, forewing vein 3r-m absent, an unusually enlarged terminal tarsomere of the midleg, and extremely elongated hindlegs. The ring of tubercles indicate that the new taxon was a parasitoid on wood-living insects. We discuss the morphology and function of the midlegs and hindlegs. We suggest that the males of this genus might have exhibited behavior similar to dance flies (Diptera: Empididae) or hangingflies (Mecoptera: Bittacidae). During mating, the males possibly used their mid legs with the expanded distal tarsus to effectively grasp and restrain the females and their elongate hindlegs to suspend themselves and their mate from the vegetation, providing support and stability during copulation.

Key words: Diptera, Kachin amber, Mecoptera, Mesozoic, morphological character, phylogenetic analysis.