This was the age of dinosaurs. 那就是恐龙时代

168. But there was one period
     但曾经有一个时期
169. when Earth was stable for 100 million years.
     地球保持了一亿年稳定状态
170. A period which allowed one group to become the mightiest of dynasties.
     这个时期 令一个物种群建立了最强大的王朝
171. This was the age of dinosaurs.
     那就是恐龙时代
172. The long calm helped dinosaurs to proliferate in huge numbers.
     长♥期♥的平静令恐龙数量激增
173. These are Maiasaura,
     这些是慈母龙
174. gentle plant eaters that form herds many thousands strong.
     温和的食植动物 数以千计 成群结队

来自《我们星球上的生命 第一季 第一集 Life on Our Planet S01E01 生命法则》第 171 行