They were all bilaterally symmetrical basket-feeders, with their upward-facing mouths positioned at one end of their bodies.

它们都是双侧对称的篮子喂食器，嘴巴朝上， 位于身体的一端。

Generally in the animal kingdom, once you evolve a bilaterally symmetrical body plan you don’t go back.

一般来说，在动物王国中，一旦你进化出双边对称的身体计划，你就不会再回头了。

Tardigrades, or more adorably known as water bears and moss piglets, are a phylum of small invertebrates that are bilaterally symmetrical and have four pairs of legs.

缓步动物，或更可爱地被称为水熊和苔藓仔猪，是一门小型无脊椎动物，它们左右对称，有四对腿。