Two new species of heptageniids (Insecta, Ephemeroptera) with long antennae from mid-Cretaceous Myanmar amber

The extant heptageniids are known as flat-headed mayflies in larval stage and mainly living in fast flowing streams. Heptageniidae is one of the most diverse family of Ephemeroptera, however, fossil Heptageniidae in Mesozoic are scarce, obscure the early evolution of this family. Herein, we report one new genus and two new species of Heptageniidae from mid-Cretaceous Myanmar amber. Longiheptagenia gen. nov. is diagnosed by the course of thoracic sutures and characteristics of venation, especially lateroparapsidal sutures are not distinctly curved laterally and without cross-veins in anal field of forewings and small number of cross-veins in the hind wings. Both of the male and female of Longiheptagenia elegantula gen. et sp. nov. are described based upon medial depression of furcasternum mesothorax narrowed anteriorly, the 5th tarsomeres longer than 1st tarsomeres in forelegs, the length proportion of tarsomeres is same in mid- and hind leg, several cross-veins and the pattern of male genitalia which is distinctly distinguished from the male of Longiheptagenia bipartita sp. nov., these findings enrich the diversity of Cretaceous Heptageniidae, moreover, provide comprehensive morphological characters to enhance our understanding of basal Heptageniidae.