The scarcity of fossils in the African rainforest. Archaeo-paleontological surveys and actualistic taphonomy in Equatorial Guinea

Abstract

The African rainforest is considered a ‘palaeontological desert’, exemplified with the virtual absence of ape fossils from the last 10 Ma. To overcome this deficiency of the fossil record, archaeo-palaeontological surveys have been undertaken in the rainforest of Equatorial Guinea. We have inventoried 225 outcrops and eluvial materials and the formation of ‘stone lines’ (of diverse genesis) predominate. Close to the Atlantic estuaries, there are short fluvial sedimentary sequences (sands and gravels), where remains of lithic industry and charcoal appear, but in no case macro vertebrate fossils. Given the intensity of the survey, the scarcity of sampling is ruled out as the cause of this ‘palaeontological desert’. Besides, biogenic, biostratinomic and fossildiagenetic factors have been explored by means of an actualistic approach. The rainforest ecosystem produces very low density tanatocenosis. Simultaneously, there is a low rate of sedimentation/erosion and the action of scavengers has not been detected, although the action of ants and termites may be determinant. Two fossildiagenetic factors can be inferred: lixiviation as a destructive cause and the existence of periods of intensive erosion. The search for palaeontological record should focus on protected sedimentary environments (rockshelters) or more confined ones (maars and small endorheic basins).