Palaeoenvironmental and palaeobiogeographical significance of the fossil rodent assemblages of Laetoli (Pliocene, Tanzania)
Abstract The study of the Laetoli rodent assemblages and comparison with other extant and fossil communities of Africa by different statistical methods provide new palaeoenvironmental and palaeobiogeographical results. Firstly, it is demonstrated that at 3.7 Myr the Laetoli assemblage belonged to a southern savanna domain and that its modern equivalent is the Kalahari rodent fauna (Namibia—South West Africa). Secondly, these analyses show that the rodent faunas from Laetoli, Hadar, Omo Member B and F (Ethiopia) and Olduvai Bed I (Tanzania), all of which are situated in the Rift Valley, are clearly distinct assemblages. Each fauna is characterized by a strong endemism and seems to have evolved independently. A tentative explanation of this observation is proposed by the examination of the structure of the Rift Valley and its evolution during Plio-Pleistocene times. Moreover, the different phases of speciation and migration of the rodent faunas can also be correlated with the tectonic events related to the formation of the Rift Valley.