from 63 million to 58 million years ago; appearance of birds and earliest mammals
造句
用作名詞(n.)
Paleontological studies showed that modern avian groups probably first appeared in the Paleocene and experienced an explosive radiation in the early Cenozoic. 古生物學研究表明，現生鳥類的最早出現是在古新世，而爆發性輻射演化發生在新生代早期。