Early Pliocene fauna from the Lower Laetolil Beds, Laetoli, Tanzania

The mid-Pliocene Upper Laetolil Beds at Laetoli in northern Tanzania have produced a rich diversity of fossil vertebrates, including the remains and traces of the early hominin, Australopithecus afarensis. The fauna from the older Lower Laetolil Beds, dating from 3.8 Ma to older than 4.3 Ma, has not previously been the subject of detailed analysis. This study, based on renewed palaeontological investigations, provides the first systematic account of the fauna, along with a brief synthesis of the geology and palaeoecology. Forty species of mammals are recorded from the Lower Laetolil Beds, dominated by bovids, equids, rhinocerotids, and proboscideans, in addition to reptiles, birds, and invertebrates. The mammal fauna is very similar to that from the Upper Laetolil Beds, and to a lesser extent to the Upper Ndolanya Beds, indicating a high degree of faunal continuity and provinciality in the Laetoli area during much of the Pliocene. Evidence indicates that the palaeoecology of the Lower Laetolil Beds was predominantly dry open woodlands-shrublands-grasslands, but dense woodlands and forests were present on the lower slopes of the nearby Satiman volcano. Water was more abundant than in the Upper Laetolil Beds, with seasonal rivers, marshes and shallow lakes bordered by riparian woodland.