Fossil legumes from the Middle Eocene (46.0 Ma) Mahenge flora of Singida, Tanzania

Middle Eocene age caesalpinioid and mimosoid legume leaves are reported fro m the Mahenge site in north-central Tanzania. The Mahenge flora complements a sparse Paleogene tropical African fossil plant record, which until now c onsisted of a single macrobotanical assemblage, limited palynological studi es in West Africa and Egypt, and fossil wood studies primarily from poorly dated deposits. Mahenge leaf macrofossils have the potential to add signifi cantly to what is known of the evolutionary history of extant African plant groups and to expand our currently limited knowledge of African Paleogene environments. The site is associated with a kimberlite eruption and demonst rates the potential value of kimberlite-associated lake deposits as much-ne eded resources for African Paleogene floras. In this report we document a r elatively diverse component of the flora consisting of the leaves of at lea st five species of Leguminosae. A new species of the extant genus Acacia (M imosoideae), described herein, is represented by a bipinnate leaf. Another taxon is described as a new species of the extant genus Aphanocalyx (Caesal pinioideae), and a third leaf type may be related to the errant genus Cynom etra (Caesalpinioideae). Two additional leaf types are less well understood : one appears to be referable to the Caesalpinioideae and subfamily affinit ies of the other taxon are unknown.