close relatives of today's deep-sea nautilus. 今天深海鹦鹉螺的近亲
like their pioneering relatives millions of years ago. 数百万年前它们富有探索精神的亲戚们 也是这样做的
It's nearest living relatives are squid and octopus which, over evolutionary time, have both lost their shells 它是已经进化到已经没有壳的章鱼和乌贼的近亲
no need for the jet propulsion used by it's shallow water relatives above. 不象它的浅海亲戚利用喷射水流的反作用力