A new species of menid fish, †Mene purdyi, is described from northwestern Peru. A Paleocene age (late Thanetian) is estimated for the specimen based on biostratigraphic analysis of planktonic foraminifers recovered from the surrounding matrix. Possible explanations for discrepancies between this result and previous interpretations of an Oligocene age are explored. Stable isotopic analysis of foraminifers associated with the fossil allows for general characterization of the thermal profile of the depositional environment. The small temperature gap between distinct depth-ecological foraminifer assemblages inferred from δ¹⁸O values indicates a low vertical temperature gradient, possibly reflecting a depositional environment dominated by upwelling. Although incomplete, the three-dimensional preservation of this specimen allows for detailed description of much of the skull, the first two vertebrae and the posttemporals. Numerous characters distinguish the new taxon from previously described menids, the most conspicuous being its exceptionally large size. Comments on the relationships of this new taxon to other menid fishes are premature until the osteology of fossil and living forms are better documented. Extinct species are briefly reviewed in order to facilitate future studies of Menidae. An examination of the distribution of fossil menids reveals that the group was once widespread, demonstrating a circum-global pattern during much of the Tertiary, consistent with the historical Tethys.