音标: 英 ['tetrəpɒd] 美 ['tetrəˌpɒd]
1. It happened to the trilobites, to the tetrapods, and then to the therapsids and the archosaurs and the dinosaurs, and guess what.
三叶虫 四足动物灭绝了 然后兽孔目动物 古蜥也灭绝了 恐龙也一样 猜猜怎么着