Late Campanian fossil of a legume fruit supports Mexico as a center of Fabaceae radiation.

Fabaceae is one of the most diverse angiosperm families and is distributed across the globe in a variety of environments. The earliest evidence of the family, previous to this work, was from Paleogene sediments where it was found to be diverse in many fossil assemblages around the world. Here, we describe a fossil legume fruit from the Olmos Formation (upper Campanian) in northern Mexico. We designated the fossil fruit as Leguminocarpum olmensis Centeno-González, Martínez-Cabrera, Porras-Múzquiz et Estrada-Ruiz sp. nov., and related it with the Fabaceae family based on the presence of a dehiscent pod with two valves, an apex bearing stylar base, short stipe, and reticulated veins in the pericarp. We propose a new fossil species of Leguminocarpum for this fossil fruit. This fossil provides critical information on the long geologic history of Leguminosae around the world, significantly extending the record into the Cretaceous of Mexico.