Paleoenvironments of Laetoli, Tanzania as Determined by Antelope Habitat Preferences

Abstract

We examined the fossil remains of antelope (Mammalia: Bovidae) postcrania recovered from the Upper Laetolil Beds and the overlying Upper Ndolanya Beds in northern Tanzania. We used analyses of the ecomorphology of extinct antelopes to determine their habitat preferences. The most common postcranial elements - the phalanges, astragali, and distal radii - were examined. A total sample of 446 specimens was analyzed. Changes in the relative proportion of habitat preferences through time are suggestive of temporal fluctuations in habitat availability. As has been noted elsewhere, the mammals from Laetoli do not show the expected distribution of body sizes, so this paper also examined how such size biases, assumed to be taphonomic in origin, might have affected the reconstructions proposed here. We conclude that, on the basis of habitat preferences of the antelopes recovered from Laetoli, there is evidence for the continuous regional presence of woodland and forest throughout deposition of the Upper Laetolil Beds. Antelopes preferring forest and heavy cover habitats dominate the assemblage. Antelopes that locomoted principally in open and light cover habitats are largely in the minority, with a combined frequency never exceeding around 25% of the total in each stratigraphic unit of the Upper Laetolil Beds. The relative proportions of heavy cover and forest preferring antelopes in particular are likely affected by body size biases caused by taphonomic processes active during the deposition of the Upper Laetolil Beds, which favoured the preservation of the postcrania of smaller antelopes. During the formation of the Upper Ndolanya Beds, the proportion of antelopes preferring more open habitats is greatly increased, although forest-preferring antelopes are still present. The conclusion that forest and woodland were always present throughout the sequence is robust.KeywordsEcomorphologyBovidaePostcranialsPliocene