Offneria simplex, nov. sp. is described from the mid Barremian. Urgonian limestones in the Vercors and Languedoc regions; it is also identified from Cuba. This is the oldest representative, known hitherto, of the genus Offneria, considered so far restricted to the early Aptian. This discovery provides new insights on the species radiation and evolution of the genus, in a well defined stratigraphic context, and its relationships with Praecaprina. This genus is characterized by independant evolutionary rates for the two valves. Its survivorship is about 4 Ma with a rate of species origination higher than 1 Ma. Offneria simplex nov. sp. has a relatively wide palaeobiogeographic distribution, from the Caribbean to western Europe and could be a biostratigraphic marker of the Barremian.