Browsing by Author "Oksanen, Otto"

The carnivoran fauna in East Africa has changed drastically over the last seven million years. Turnover in the fauna affected taxonomic composition during the Miocene-Pliocene boundary, as well as led to both reduced species richness and functional richness from 3 Ma ago onwards until the modern fauna was in place. The objective of this thesis was to examine how the niche space in the East African carnivore guild has changed over time by making inferences on the feeding ecology of individual taxa from two sites located in the Turkana Basin, a major depository of vertebrate fossils in northern Kenya. The first site, Lothagam, covers the time slice 7.4–5.3 Ma ago, whereas the second site, Koobi Fora, covers the time slice 3.4–1.38 Ma ago. An ecomorphological analysis was performed, which included dental ratios, body mass estimates and jaw measurements of carnivorans, as well as body mass estimates of some of their potential prey animals (bovids). The carnivorans were assigned to four different dietary specializations based on their dental ratios: hypercarnivore, bone-cracking hypercarnivore, mesocarnivore and hypocarnivore. Individual taxa were also identified as small-prey or large-prey specialists based on their body mass estimates and jaw depth. According to the results, the carnivore guild of Lothagam was mostly composed of hypercarnivores along with some mesocarnivores that were trending towards hypercarnivory. There is a notable absence of hypocarnivores and bone-cracking hypercarnivores in the Lothagam sample. The carnivorans of Koobi Fora displayed more variation in the dental ratios between individual taxa. Compared to the Lothagam guild, the Koobi Fora guild also included advanced bone-cracking hypercarnivores, as well as large hypocarnivores that are absent from East Africa today. The changes in the dietary specializations of individual Koobi Fora taxa were accompanied by an overall increase in body size, which coincided to some extent with an increase in prey size, at least with bovids. The results indicate that some of the extinct members of the carnivore guild became more ecologically specialized during the Plio-Pleistocene, which probably made them more vulnerable to extinction than the more generalized taxa during changing environmental conditions.