Leviathanochelys and Archelon could have been the biggest examples in this process.

在这个过程中，利维坦巨龟和古巨龟可能是最大的例子。

In fact, Archelon didn't even make it out of the Cretaceous.

事实上，Archelon 甚至没有走出白垩纪。

Like the leatherback, Archelon didn't have a hard upper shell, or carapace.

与棱皮龟一样，Archelon 没有坚硬的上壳或甲壳。

Both Archelon and its cousin Protostega were gone before the Cretaceous Period even ended.

Archelon 和它的表亲 Protostega 在白垩纪结束之前就消失了。

Leviathanochelys nearly matched the largest turtle on record - Archelon, which lived roughly 70 million years ago and reached about 4.6 meters long.

利维坦巨龟几乎与有记录的最大海龟——古巨龟不相上下，古巨龟生活在大约7000万年前，体长约4。6米。

One of these transitions included the group of sea turtles that Archelon belonged to - the protostegids - whose fossils have been found in Europe, Australia, and South America.

这些转变之一包括 Archelon 所属的海龟群——原龟类——它们的化石已在欧洲、澳大利亚和南美洲被发现。

And, at around 4.5 meters long and weighing more than two metric tons, Archelon -- as it's known -- was more than twice the size of the largest sea turtle today - the leatherback.

而且，Archelon 长约 4.5 米， 重量超过两公吨，是当今最大的海龟棱皮龟的两倍多。