Members of the legume family are one of the most important plant components of the extant Mexican vegetation. However, the history on how this group of plants became established and diversified in this geographic area is just being assembled through phylogenetic and biogeographic analyses based on extant plants. Fossil plants collected during the last decade support that the family was present in NE Mexico since at least the Middle Eocene, and suggest that by the Oligocene, legumes were a common element of the emerging region. Though, cuticles have not been recovered from the new material, morphological comparison of fruits and leaflets strongly suggest the presence of members of Robineae (Robinia and Poitea), Ingeae (Inga, Pithecellobium, Chloroleucon, Zapoteca or Calliandra), Cassieae (Senna) and confirm the presence of other tribes like Mimoseae (Mimosa) and Detarieae (Hymenaea). These new records add to the known diversity of the family in North America and tend to support the biogeographic findings based on extant plants, suggesting that during the Tertiary the boreotropical flora extended its distribution to southern Mexico.

Key words: boreotropical flora, fossil, Leguminosae, Mexico, Oligocene, Tertiary