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The giraffid fossils recovered from~2.8-2.6 million year old (Ma) sediments from Lee Adoyta, Ledi-Geraru, Ethiopia, are described here. Sivatherium maurusium and Giraffa cf. G. gracilis are the two identified taxa, with the former being more abundant than the latter. We interpret this skew of relative abundance to be of paleoenvironmental significance, as Sivatherium is rare and Giraffa is common in the adjacent, but older sediments of the Hadar Formation at Hadar (~3.4 to 2.95 Ma), which was characterized by wooded and well-watered habitats through most of its sequence. Stable carbon isotope analyses show that Giraffa remained an obligate browser throughout the lower Awash Valley (LAV) sequence while Sivatherium underwent a dietary transition from a browser in the Hadar Formation to a grazer at Lee Adoyta. This dietary shift in Sivatherium reflects local environmental change through time in the LAVas open habitats spread during the late Pliocene. A compilation of isotopic data from other sites in eastern Africa shows that the LAV dietary shift in Sivatherium occurred roughly one million years earlier than in the Turkana Basin, Kenya, reflecting a spatiotemporally staggered expansion of C 4 vegetation across eastern Africa.

Early Miocene carnivorous mammals from Buluk, Kenya, are described and discussed. Four taxa belonging to Hyaenodonta and four belonging to Carnivora are identified. Members of Hyaenodonta include Hyainailouros sulzeri, Hyainailouros cf. napakensis, a third taxon about the size of Leakitherium, represented only by postcranial material, and a fourth taxon represented by an edentulous jaw, in the size range of Sectisodon. Members of Carnivora include a new species of Cynelos jitu, which represents the largest species of Cynelos known. The first m2 of Cynelos macrodon is described, and the differentiation of this species from Cynelos ginsburgi and Cynelos peignei is confirmed. A third carnivoran species is represented by a mandibular fragment attributed to a viverrid similar to Mioprionodon, and a fourth taxon is represented by a feliform distal humerus, the size of that of a small cat. An ecomorphological guild structure analysis reveals that the Buluk carnivore have estimated body sizes spanning from 100 kg. Three very large species (>100 kg), and another two in the 30-100 kg range are present, while only two taxa are present in the 3-10 kg category. Carnivores in the 1-3 kg and the 10-30 kg categories are absent. Locomotor pattern could be obtained for only four taxa, and all are characterized by terrestrial locomotion. A minimum of three dietary classes (insectivorous, carnivorous, scavenging) are represented. The co-occurrence of multiple very large carnivores is not uncommon in early Miocene faunas, but the taphonomy of Buluk may also contribute to the favored preservation of larger and terrestrially adapted animals.