But all of them forced to the margins by the dominance of the dinosaurs 但所有这些动物 都被统治者恐龙逼到边缘
But kangaroo rats are not your average rodent. 但是更格卢鼠可不是普通的啮齿动物
But mammals have acquired some extraordinary defenses... 但是哺乳动物与蛇的军备竞赛 已经开展超过一亿年
But the snake is headed straight for her youngster. 但是蛇直扑幼崽
But young mammals aren't entirely helpless. 但是哺乳动物幼崽并非完全无助
But for these nervous little youngsters... 但对于这些紧张的幼崽们来说
But they, too, were becoming increasingly sophisticated, social, 但它们也变得越来越复杂 有社会性
...but they had evolved jaws that could chew. 但它们已经进化出能够咀嚼的颌部