By JULIA DUIN | Special To The Washington Post | Published: December 10, 2020 Prehistoric Oregon was a lush refuge for a zoo s worth of exotic animals, which flourished amid tropical fruits, palm trees and a climate much like present-day Panama from 55 million years ago to 39 million years ago. Avocados and bananas were plentiful, and mammals such as oreodonts (piglike creatures); brontotheres, (a combo of horse and rhino) and a kind of mastodon called a zygolophodon had the run of the place because dinosaurs had disappeared from the world more than 15 million years earlier. Other than the volcanic blasts that would cover the region with hundreds of feet of lava and ash and wipe out all living things every 15,000 years or so, life was good.