And that was the end of that first group of giant, skin-shelled turtles -- the protostegids.

这就是第一批巨型皮壳龟——原龟的终结。

Just like the protostegids did 50 million years earlier, this group diversified and spread around the world, their fossils found in deposits from Japan to the UK.

就像 5000 万年前的原生动物一样，这个群体多样化并传播到世界各地，他们的化石在从日本到英国的沉积物中被发现。

And some of the earliest protostegids had bodies like Archelon's: big, with lightweight shells, which may have let them travel long distances and spread out around the world.

一些最早的原生动物拥有与阿奇隆相似的身体：大而轻的外壳，这可能让它们能够长途跋涉并散布到世界各地。