from 63 million to 58 million years ago; appearance of birds and earliest mammals
例句
用作名词 (n.)
Paleontological studies showed that modern avian groups probably first appeared in the Paleocene and experienced an explosive radiation in the early Cenozoic. 古生物学研究表明,现生鸟类的最早出现是在古新世,而爆发性辐射演化发生在新生代早期。