The Leguminosae has a diverse and abundant fossil record, which has been well documented from numerous Tertiary age localities, primarily in North America, Europe, and Asia. The record from these areas shows a sudden appearance of diversity in the middle Eocene. The available fossil data have been useful in providing minimum ages of clades within the family and in providing historical context for modern biogeographic patterns. However, several holes exist in the known record, one of the most significant being a lack of fossils from low paleolatitudes. The fossils described in this paper are significant therefore because they are from the Eocene of Tanzania. The fossils were recovered from lacustrine sediments from the Mahenge site (Singida District) in central Tanzania. The deposit represents a small paleolake that formed in a kimberlite eruption crater. The fossil plant assemblage is strongly dominated in taxonomic diversity and abundance by members of the legume family, which is represented by fossil leaves and fruits. The Caesalpinioideae is documented by leaves of several taxa, including the extant genus Aphanocalyx, which includes ca. 15 species primarily in western and central tropical Africa today. Fossil leaves of another caesalpinioid taxon are similar to leaves of the extant genera Cynometra, Julbernardia, and Guibourtia, but precise relationships remain to be determined. The Mimosoideae is represented by at least two taxa, one of which is the genus Acacia. There are no confirmed papilionoids in the assemblage. Also present are two types of legume fruits, one of which is moniliform and most specimens show evidence of seed predation, possibly by bruchid beetles. Thus the Mahenge site is a valuable addition to our understanding of the fossil history of the Leguminosae by providing much needed insight on legume diversity at low latitudes during the early Tertiary.

Key words: Africa, Eocene, Leguminosae, Tertiary