their hard exoskeletons had served as useful armor underwater. 坚硬的外骨骼在水下是有用的护甲

55. created new habitats for the next invaders from the sea.
    为来自海洋的下一批入侵者 创造了新的栖息地
56. The first animals to ever set foot on land were the arthropods.
    率先踏上陆地的动物是节肢动物
57. Relatives of the trilobites,
    它们是三叶虫的亲戚
58. their hard exoskeletons had served as useful armor underwater.
    坚硬的外骨骼在水下是有用的护甲
59. On land, that armor supported them
    在陆地上 这护甲支撑着它们
60. and prevented them from drying out.
    并防止水分流失
61. They could also breathe through this tough exterior.
    它们也可以通过这坚硬的外壳呼吸

来自《我们星球上的生命 第一季 第三集 Life on Our Planet S01E03 入侵大地》第 58 行