Cenozoic Earth - Brontotherium with birds

Location South Dakota, USA 35 million years ago Mean atmospheric O₂ 130% of modern level Mean atmospheric CO₂ 2x pre-industrial level Mean temperature 4°C above modern level		Geologic Time Scale Era: Cenozoic Period: Paleogene Epoch: Eocene Age: Priabonian

	Brontotherium with birds Odd-toed ungulate mammals of the genus Brontotherium wander the lush Late Eocene landscape of South Dakota 35 million years ago. Modern rhinoceroses have a symbiotic relationship with birds (variously known as oxpeckers or tick birds) that eat parasites they find on the rhino's skin and noisily warn of danger. No doubt similar symbiotic relationships existed between birds and the megafauna of the Eocene.