The oligocene was a time of changing environments  and the forests proailurus originated gradually turned into grasslands.

渐新世是一个环境变化的时期，起源的森林逐渐变成了草原。

And by the start of the Oligocene epoch, about 35 million years ago, giants like Paraceratherium measured a whopping 4 to 6 meters tall at the shoulder and around 7.5 meters long.

在大约 3500 万年前的渐新世初期，像 Paraceratherium 这样的巨人的肩高高达 4 到 6 米，长约 7.5 米。