The genus Diplocynodon is widely recorded in Europe from Early Eocene up to Middle Miocene times. A fragmented but almost complete skull of a new species of Diplocynodon is reported from the Late Eocene locality of Domérat, northern border of the Massif Central (Allier), France. The present skull provides an important basis for comparison with other members of the genus and complements a fossil record full of gaps despite the large number of vertebrate localities spanning the Cenozoic. The new taxon occurs at a key period for climate evolution with conditions marking the transition from a greenhouse to an icehouse world. The response of crocodylian assemblages to this climatic shift is discussed in light of evidence for their decline in diversity from the Eocene period onward.