AUTHOR=Bernor Raymond L. , Cirilli Omar , Jukar Advait M. , Potts Richard , Buskianidze Maia , Rook Lorenzo 

TITLE=Evolution of Early Equus in Italy, Georgia, the Indian Subcontinent, East Africa, and the Origins of African Zebras

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=7

YEAR=2019

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2019.00166

DOI=10.3389/fevo.2019.00166

ISSN=2296-701X

ABSTRACT=<p>We report here ecological and morphological characterization of the main Old World <italic>Equus</italic> in North America, Asia, Europe, and Africa, by comparing the studied fossil forms with the living <italic>Equus grevyi</italic> zebra. <italic>Equus simplicidens</italic> from North America, <italic>Equus livenzovenzis, Equus stenonis</italic>, and <italic>Equus stehlini</italic> from Italy, <italic>Equus sivalensis</italic> from India, <italic>Equus</italic> cf. <italic>stenonis</italic> and a small <italic>Equus</italic> from Georgia (Caucasus), <italic>Equus oldowayensis, Equus koobiforensis</italic>, and <italic>Equus</italic> cf. <italic>tabeti</italic> from Kenya and the extant <italic>Equus grevyi</italic> are described in their cranial and dental features and are compared in morphological postcranial dimensions by means of log10 ratio analysis. The occurrence of the two horses at the Dmanisi <italic>Homo</italic> site in Georgia is reported here for the first time. Our comparative analyses allow to confirm the primitive lineage of the ancient zebras as derived from <italic>Equus simplicidens</italic>, and the successive evolution of the stenonine horses in Asia, South Asia, and Europe during the Plio—Pleistocene. The morphological analysis has reveals a clear trend in third metacarpals and third metatarsals of <italic>E</italic>. <italic>simpicidens</italic>, the small <italic>Equus</italic> from Dmanisi and <italic>E</italic>. <italic>grevyi</italic>, suggesting a close relationship between these species. The trend of the stenonine <italic>Equus</italic> from Europe and Asia confirms the possible derivation from the North America <italic>Equus simplicidens</italic>. The description of all the Old World <italic>Equus</italic> is integrated with an overview of their paleoecological context, with a referred section for each locality where these fossils were found. This contribution represents a comprehensive review of the present knowledge of the Old World <italic>Equus</italic> evolutionary history, with some new important data in deciphering the deep origin and evolution of ancient and living zebras.</p>