A completely preserved cockroach Sociala perlucida gen. et sp. nov. ?(Blattida: Socialidae fam. nov.)? is described from the Mesozoic (Albian Early Cretaceous) amber of Archingeay in France. It is categorized within the new family Socialidae, originating from the Mesozoic cockroach family Liberiblattinidae, and representing the sister group to the most basal known eutermite families. Numerous direct and indirect morphological evidence (such as a unique narrow body and pronotum with reduced coloration, legs without carination and with numerous sensillar pitts (forelegs) as adaptations to life in nests analogical to the living termitophillous species; enlarged head, long palps for communication, a general venation modified in a direction towards termites (subcosta and radial vein [R] approximated, R branches approximated, simplified, cross-veins reduced), and possibly also the development of the breaking forewing sutura for detaching wings after marriage flight), suggest its eusocial mode of life. Thus, the first eusociality originated within cockroaches, prior to giving birth to termites; termites and Cryptocercus are not directly related. The group of eusocial cockroaches makes termite morphotaxon polyphyletic, but also in this case, the erection of a new order for mastotermites (including Cratomastotermitidae) and/or the inclusion of eusocial, morphological cockroaches within termites appears couterproductive, thus an example of such a general exception to the taxonomical procedure is provided.