The first one occurred around 150 million to 140 million years ago during the Mesozoic era.

第一次发生在大约1.5亿至1.4亿年前的中生代。

By studying these ancient clues, paleontologists piece together the puzzle of the Mesozoic era.

通过研究这些古老的线索，古生物学家拼凑出了中生代的谜团。

Over the vast epochs of the Mesozoic era--the Triassic, Jurassic, and Cretaceous periods--dinosaurs evolved into myriad forms.

在中生代的漫长时期——三叠纪、侏罗纪和白垩纪——恐龙进化成了无数的形态。

During much of the Mesozoic era, the world was warmer than today, with no polar ice caps.

在中生代的大部分时间里，世界比今天温暖，没有极地冰盖。

A Symphony of Evolution While dinosaurs are the poster creatures of the Mesozoic era, they were far from the only inhabitants.

进化的交响曲虽然恐龙是中生代的标志性生物，但它们远非唯一的居民。

And these turned out to be the most common and diverse group of birds in the whole Mesozoic era, filling many of the same roles as modern birds.

事实证明， 这些鸟类是整个中生代最常见、最多样化的鸟类群，扮演着许多与现代鸟类相同的角色。