Newly discovered cercopithecid, equid and other mammalian fossils from the Chorora Formation, Ethiopia

Abstract

The vertebrate fossil localities of the Chorora Formation, Ethiopia, comprise one of only a few sub-Saharan African paleontological research areas that illuminate Late Miocene African mammalian and primate evolution. Field work at Chorora since 2007 has resulted in the establishment of new vertebrate fossil localities and a revised chronostratigraphic framework. The new Chorora Formation fossils include the earliest known records of Cercopithecinae, Hippopotaminae, and Leporidae in Africa. Two lineages of hipparionins are recognized at Chorora, a larger and smaller morph, forming potential phyletic links between the earlier Samburu Hills hipparionins and later Eurygnathohippus turkanensis and E. feibeli from Lothagam, Kenya. The Chorora colobines are larger than the >9 Ma Microcolobus and morphologically conservative with only moderate molar cusp notches. The Chorora cercopithecines represent the earliest documented occurrence of the subfamily.