Hipparions are an extinct group of three-toed horses that flourished widely in the Old world shortly after their first occurrence there in the late Miocene, at about 11 Ma. Once established, hipparions evolved into a multitude of lineages with chronologic ranges extending to the middle Pleistocene in China and the late Pleistocene of Africa. The paleobiology of these horses within this great temporal (ca 10 m.y.) and geographic span has not been addressed systematically heretofore. PIs believe that hipparions actually originated within the North American genus Cormohipparion, but the actual species involved has not been demonstrated. Their proposed research will break new ground in 1. describing a complex pattern of speciation within Cormohipparion; 2. better resolving the Old World hipparion immigration and subsequent evolutionary radiation; and 3. unraveling the origin, evolutionary radiation, multiple geographic extensions and adaptation of species belonging to a distinctive Old World late Miocene Pleistocene radiation known as the Sivalhippus Complex. Once having described and documented the pattern of dispersal and diversification of hipparions in the Old World PIs will be able to investigate the paleobiology of these horses to gain further insights on the dietary and locomotory adaptations by which they achieved their predominance in this evolutionary theater for so long an interval of time.
The PI has undertaken a multi-decade investigation of the origin, evolutionary radiation and intercontinental extension of 3-toed horses. He has studied these horses from North America, Europe, Asia, the Indian Sub-Continent and Africa. EAR0125009’s emphasis was on utilizing a large quarry sample of 3 toed horses of the species Hippotherium primigenium (Hegau, Southern Germany, 10.3 million years old) as a population sample standard to precisely identify species of hypsodont horses, characterize their unique morphologic attributes and study their chronologic and biogeographic ranges as well their functional anatomical and ecological adaptations. This grant allowed the PI to make important scientific advances in understanding what the major evolutionary lineages of hipparionine horses were and their evolutionary characteristics. Patterns of gradual evolution have been identified in the Central European late Miocene Hippotherium primigenium and the late Miocene and early Pliocene Eurygnathohippus feibeli – Eurygnathohippus hasumense clade of East Africa. Patterns of rapid evolution and genuine "punctuated equilibrium" have been identified in the early late Miocene of Turkey Sinap hipparion fauna. Hipparionine horses have been found to evolve endemically in some circumstances such as the Central European late Miocene and to have undergone great range extension as is characteristic for the genera Cremohipparion (pan-Eurasia and North African range) and members of the "Sivalhippus" Complex (South and East Asia and Africa). Lineage-based research as practiced in our Collaborative Research project on the Evolutionary History of Holarctic and Ethiopian Horses: Systematics, Lineage Extensions and Adaptations is multidisciplinary in nature and has successfully integrated geological, paleontological, biological and ecological sciences to better understand the relationship between paleoclimatic change, organismal response and mechanisms that regulate intercontinental geographic range extension and isolation. Broader impacts of this project have included training a foreign graduate student, Dr. Dominik Wolf, who received his PhD in December 2011 for his dissertation on the evolution of Siwalik (Indian SubContinent) Hipparions, training students from other institutions (Dr. Robert Scott, University of Texas, Austin, now Rutger’s University and Dr. Thomas Kaiser, University of Frankfurt, now University of Hamburg, Germany), collaboration with numerous colleagues, both American and Foreign and developing new professional standards for study, measurement and statistical analysis of all skeletal elements of hypsodont equids. The PI has developed an equid specimen-measurement database including more than 15,000 records that has been made available to national and international researchers. The PI continues to contribute to the Neogene Old World Database (NOW Database, Helsinki, Finland, Professor Mikael Fortelius, Director) and the Revealing Hominid Origins Initiative Database (RHOI, Berkeley California, Professor Tim White, Director) as expert on extant and fossil horses and large mammals. The PI thanks NSF for its continued support of this research.
