New dance flies from Burmese amber providing the new insight to early evolution of feeding habits in Atelestidae (Diptera: Empidoidea)

The superfamily Empidoidea is a megadiverse group of Diptera that exhibits abundant morphological specializations for predatory feeding habits, with the mouthparts unequivocally representing the core apparatus and are highly associated with feeding behaviors. Nevertheless, the evolution of feeding habits in Empidoidea was not well documented especially due to the rarity of fossil evidence at the early stage. We describe a new genus with two new species of Atelestidae, namely Promeghyperus muricicaudatus Zhang, Shih, Ren et Wang gen. et sp. nov. and P. hirtus Zhang, Shih, Ren et Wang sp. nov. from the mid-Cretaceous Burmese amber. Details of mouthparts were well-preserved in the specimens of P. muricicaudatus gen. et sp. nov. that allows for a morphological functional analysis. The results reveal that these two mid-Cretaceous atelestid species retain the well-defined epipharyngeal blades and evolve a predaceous feeding habit in contrast to their extant relatives. The evolution of epipharyngeal blades in Empidoidea is summarized under the current phylogenetic framework. This finding not only enhanced the knowledge of species diversity of Empidoidea during the mid-Cretaceous but also provided the key evidence to document the evolution of feeding habits among Empidoidea. Based on the analysis of palaeogeographic occurrences of fossil and extant lineages, the evolutionay history of Atelestidae is outlined.