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Fifteen new legume taxa based on fruits and foliage, including 10 Mimosoideae (three Inga spp., two Pithecellobium spp., Acacia, Mimosa, two Stryphnodendron spp., and Piptadenia), three Caesalpinioideae (Chamaechrista, Senna, and Apuleia), and two Papilionoideae (Cladrastis and Robinia), are described from the Eocene San José de la Popa locality, La Carroza Formation, Nuevo León, and the Oligocene Los Ahuehuetes locality, Coatzingo Formation, Puebla, Mexico. Comparing the fruit type of the Leguminosae and the leaf architecture of the family with the fossils here studied, it is possible to confirm the presence of Leguminosae in Mexican territory (= low-latitude North America) since the Paleogene and to suggest that the family has been an important element of its flora and vegetation through the Cenozoic. The place of origin of the family is uncertain, but the diversification of some lineages through the Tertiary in North America is well supported by the fossil record. Furthermore, as the fossil record is complemented with phylogenetic studies, the importance of North America, including Mexico, as an area of diversification of plants phylogenetically related with European, Asian, and even African ones is further supported. The new fossil legumes are in part consistent with the concept of a Tertiary boreotropical flora that extended southward into Mexico, as well as with the recognition that some taxa likely evolved in low-latitude North America rather than merely arriving as immigrants from adjacent regions. [ABSTRACT FROM AUTHOR]