Bovids as palaeoenvironmental indicators : an ecomorphological analysis of bovid post-cranial remains from Laetoli, Tanzania
This thesis reports on 1) a new method of palaeoenvironmental reconstruction using bovid ecomorphology and 2) the application of this methodology to fossil assemblages from the Plio-Pleistocene site of Laetoli, Tanzania. A global saniple of extant bovids (n205), cervids (n=14) and tragulids (n=5) from seven known habitat types comprise the comparative dataset. All long bones, carpals, tarsals and phalanges are measured. These measurements are entered as predictor variables in discriminant function analyses (DFA) in order to evaluate the ability of each element to accurately predict habitat affiliation. The baseline of chance accuracy for DFAs (i.e. the percentage of correct predictions that can be expected when habitat assignments are randomised) is determined. This baseline serves as the cut-off point between good and bad habitat predictors. Analyses are conducted on non-size corrected and size corrected data. The results of both sets of analyses are similar. A total of 24 analyses of non-size corrected elements and 23 size corrected analyses yield percentages of correct classification over the baseline of accuracy. The non-size corrected analyses are extended to the Laetoli fossil assemblages. DFAs are conducted on fossil assemblages from the Upper Laetolil Beds (3.50 - 3.80 mya) and the Upper Ndolanya Beds (2.66 mya). Summaries of the number of specimens predicted to belong to each habitat type and their associated probabilities of correct prediction are used to reconstruct the palaeoenvironrnent. The results indicate that at the time of the deposition of the Laetolil Beds the area had heavy woodland-bushland cover with some lighter tree and bush cover and grass available. This lends strong support to recent suggestions that the area was on the more wooded end of the habitat spectrum, contra initial conclusions that it represented a mosaic of more open habitats. It furthermore supports the theory that early australopithecines such as Au.siralopiihecies afiiren,s'is required a significant amount of tree cover for survival. The results also indicate that during the deposition of the Ndolanya Beds the environment had become more open and the grassland component of the environment had increased significantly. Light woodland-bushland and an abundance of grass cover dominated the landscape, although tracts of land with denser vegetation likely existed. This agrees with earlier suggestions that the area was a semi-arid bushland. It also supports the theory that Paranthropus aethiopicus was adapted to a lifestyle in a more open and arid environment than earlier species.