今天的地球上生活着千奇百怪的动物,向前追溯,它们都有自己的动物祖先。当我们要寻找地球上最早出现的动物时,我们会碰到很大的麻烦。因为地球上的第一只动物显然已经消失在地球的往事尘烟中,它的许多后代也早已寿终正寝。虽然古生物学家可以通过岩石里的化石探索动物的祖先,但是化石记录往往缺失严重,而且许多古老的动物都是软躯体的,很难保存成化石。 Today there are a myriad of strange animals on Earth, going backwards, all of whom have their own ancestors of animals. When we look for the earliest animals on Earth, we have a great deal of trouble. Since the first animal on Earth apparently disappeared into the dust of the earth, many of its descendants had already come to an end. Although paleontologists can explore the ancestors of animals through fossils in rocks, fossil records are often absent, and many ancient animals are soft bodies that are difficult to preserve as fossils.