Abstract
The monophyletic mayfly family Vietnamellidae has been introduced for a few extant species from the Indomalayan Realm. All these species belong to the genus Vietnamella and have been described in adult and larval stages. Recently, the fossil genus Burmella was established for male and female imagines of two new species from mid-Cretaceous Burmese amber and assigned to the family Vietnamellidae. In this contribution, we describe another species in the genus Burmella, namely B. inconspicua sp. nov. based on a female imago. It clearly differs from the previously described female of B. clypeata by the absence of an extension of the clypeus and by a different venation in fore and hind wings. Furthermore, we discuss here in detail the systematic position of the monotypic species Burmaheptagenia zhouchangfai originally assigned to the family Heptageniidae and provide arguments for the synonymy of the genus Burmaheptagenia syn. nov. with Burmella. We propose the new combination Burmella zhouchangfai comb. nov., together with a modified generic diagnosis for the genus Burmella and discuss the adult characters of Vietnamellidae. Systematic placement of the genus Burmella in Vietnamellidae and the phylogenetic position of this family within Ephemerelloidea are discussed. We also consider the geographic origin of the family and the role of the Cretaceous Burma Terrane migration as a key event that facilitated the transfer of Gondwanan fauna to Asia.