FOSSIL LEGUME FRUITS FROM TERTIARY STRATA OF PUEBLA, MEXICO

Abstract

Mimosoideae), Mimosa (Mimoseae

Mimosoideae), Lysiloma (Ingeae

Mimosoideae),and Sophora (Sophoreae

Papilionoideae). Another fruit exhibits a combination of characters unknown among extant legumes, and although superficially similar to some species of Papilionoideae, it represents an extinct genus. The four identified genera are diverse in the extant vegetation of Mexico

in fact, Mexico represents an important area of distribution for them. The presence of Prosopis, Mimosa, Lysiloma, and Sophora in the fossil flora of Puebla documents the occurrence of these genera in this part of their present area of distribution by the Oligocene. The climatic affinities of modern species of Mimosa, Lysiloma, and Sophora are so varied as to preclude any useful paleoclimatic inference. Prosopis is regularly associated with arid environments

however, the genus has been reported from fossil localities where humid conditions prevailed. This observation, together with the assemblage of plants that co-occur in the Los Ahuehuetes flora, suggests that plant communities of the past may have been composed, at least partly, of elements that today are associated with different habitats and environmental conditions. The fossil legume fruits from Los Ahuehuetes flora add to the previously known diversity of Leguminosae by the Tertiary, confirm tropical America as one of the important areas of radiation and diversification for Leguminosae, and contribute to the knowledge of Tertiary floras of southern North America.

A small assemblage of fossil legume fruits, leaf fragments, and leaflets has been recovered from the Tertiary (Oligocene) ''Los Ahuehuetes'' flora near the town of Tepexi de Rodríguez, Puebla, in south-central Mexico. Five legume fruits are described and compared with fruits of extant genera. Four fruit types were identified as belonging to the modern genera Prosopis (Mimoseae