21. Uplift started in the Oligocene and lasted till the Pleistocene. 22. Camels were a new arrival to Nebraska during the Oligocene . 23. Fossil Prionomyrmecini ants existed in Europe during the Eocene and Late Oligocene . 24. Ore deposits occurred mainly along major mineralization occurred in the Late Oligocene . 25. Sag phase deposition begins in the upper Eocene to Oligocene . 26. In the region, mafic volcanism has been active since the Oligocene . 27. The first cats emerged during the Oligocene , about 25 million years ago. 28. Perissodactyls were the dominant group of large terrestrial browsers right through the Oligocene . 29. There are two phases of extension observed : late Oligocene and middle Miocene. 30. In the Oligocene , they are found in these three regions plus Africa.
