Paleoecology and body mass distribution of horses in northern Eurasia during the Pleistocene

The “grazing horses″ (Equinae) were successful large herbivores that arrived from North America to Eurasia at the Plio–Pleistocene boundary. The adaptiveness of high-crowned (hypsodont) Equus spp. allowed them to conquer environments from open to forested, resulting in different body sizes. Few large-scale studies on horse body mass in northern Eurasia exist. Despite controversial systematics of Equidae, their ecomorphological features are quantifiable. The Pleistocene habitat and Equus spp. body mass changes were studied across northern Eurasia. Mean non-equid ungulate hypsodonty demonstrated progressive opening of landscapes throughout the Pleistocene, returning towards more humid and closed environments (taiga) below 70°N by the Holocene. Landscape heterogeneity across northern Eurasia indicated different zoogeographic provinces. Mean Equus spp. body mass decreased during the Middle Pleistocene to resemble the Holocene estimates. The Holocene domestication might have prevented small-sized and grazing-adapted horse lineages from extinction when taiga forests spread across northern Eurasia.