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The criteria used for the identification of species and genera of Cenozoic large benthic Foraminifera strongly affect interpretations of their geographic distribution. Some researchers contend that migration of large forams between west Africa and the Americas became impossible after the middle Eocene because of increased distance and of ecologic barriers. Thus, the discovery of the Eocene genus Linderina in west Africa led them to conclude that the cosmopolitan Tertiary genus Lepidocyclina evolved from Linderina in the Old World, whereas it evolved separately from Eulinderina in the Americas. We find it difficult to accept these conclusions, especially in view of the number of Tertiary species of Lepidocyclina and Miogypsina which are common to the Mediterranean area, Af ica, and the Americas. The discovery of additional large foraminiferal species common to west Africa and the Americas supports our view that many species of Oligocene and Miocene large Foraminifera had much greater paleobiogeographic distribution than has been generally realized.
Carbonate buildups dominated by floods of Heterostegina have been widely reported from the upper Oligocene and lower Miocene of the Caribbean-Gulf of Mexico region. We have recently discovered much of the large foraminiferal fauna of these so-called "Het reefs" in the upper Oligocene and lower Miocene of Cameroon (west Africa). Included are such typical Caribbean species as Leipdocyclina canellei. The species of Miogypsinoides present in the sequence may represent an evolutionary trend different from those in other parts of the world. They appear to be most closely related to the Caribbean species Miogypsina panamensis. In addition, we have found Operculinoides cojimarensis in the upper Miocene of Gabon. This species occurs abundantly from middle Miocene to lower Pliocene rocks in the Caribbean area and represents the end of the nummulitid evolutionary lineage in that region. Its presence in west Africa is further indication that communication persisted between west Africa and the Caribbean at least as late as the late Miocene.
Moreover, a surprisingly large number of species of smaller benthic Foraminifera is common between west Africa and the Caribbean. The literature records an apparent scarcity of species of large Foraminifera common to both the New and Old Worlds. This apparent scarcity suggests that the parameters used to identify these species are not appropriate and should be reviewed.
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