Microhymenopterans are important components of modern ecosystems, where they act as egg parasites and hyperparasites of arthropods. Mymarommatoidea are among the smallest hymenopterans and their actively flying adults have four wings, like all known members of the order Hymenoptera. Mymarommatoids were first described as fossils, and although their extant 12 species are distributed worldwide, little is known about their biology. They seem to be absent from the tropics presently, and only two species in two families of Mymarommatoidea are known from the tropical mid-Cretaceous Burmese amber. Here we describe a new family, Dipterommatidae fam. nov., the fourth in Mymarommatoidea, with a single genus and species Dipteromma paradoxa gen. et sp. nov., based on a female from the same source. The fossil is unique in the superfamily and in the whole order Hymenoptera in totally lacking the hind wings. The complete loss of the hind wings in an actively flying insect is rare. Among the few examples is a bloodsucking mecopteran Parapolycentropus, another bizarre endemic taxon of the rich mid-Cretaceous Burmese biota. (C) 2019 Elsevier Ltd. All rights reserved.