A mammal that had adapted well to the more open scrubland of the northern hemisphere of this period was the Brontothere. They were like oversized rhinos, with a bony outgrowth on their nose. They belonged to the same order as today's horses, rhinoceroses and tapirs, but are probably closest related to horses. They roamed the scrublands in huge herds, browsing the lower tree branches, shrubs and soft vegetation. There were several different species, some as big as elephants and weighing two tons. Fossils have been found in Mongolia and Wyoming, USA. (15)
The end of the Eocene was marked by another mass extinction event where almost 20% of all living things on earth died out. If it was only the sudden change in climate or if other factors like another meteorite where at play, we do not know.