The next one happened about 100 million years later during the Cenozoic era, after the extinction of the dinosaurs and the rise of mammals.

下一次发生在大约1亿年后的新生代，当时恐龙灭绝和哺乳动物崛起。

For example, let's assume the nonavian dinosaurs had the same ratio of big species to small ones as the extinct land mammals of the Cenozoic era did.

例如，我们假设非鸟类恐龙的大型物种与小型物种的比例与新生代灭绝的陆生哺乳动物相同。