Ankylosaurus represents the end of the history of the armored dinosaurs, the ultimate in dinosaurian tanks.
甲龙代表了恐龙家族中装甲恐龙的终结，是恐龙坦克中的顶峰。
But some dinosaurs don't rely on body armor and weapons for defense.
但有些恐龙并不依靠护甲或者武器来自卫。
They have an entirely different strategy-- grow bigger. Much, much bigger.
它们有一种完全不同的策略长得更大。非常庞大。
Montana, America. It's not called the Wild West for nothing.
美国，蒙大拿。"荒蛮西部"并非徒有虚名。
Hungry predators are everywhere.
饥肠辘辘的捕食者随处可见。
In response, prey developed an incredible array of defensive strategies.
对此，猎物们也想出了各种各样奇特的防卫策略。
Strategies that don't rely on intelligence, but on physical traits.
这些策略并不依靠智力而是依靠身体。

Sauroposeidon is a gargantuan beast, growing to 50 tons or more.
波塞东龙是一种庞然巨兽体重超过五十吨。
Sauroposeidon was one of the largest animals that ever lived on land.
波塞东龙是当时体型最大的陆生动物之一。
If you're gigantic, there are fewer and fewer predators that can attack you.
如果你体型庞大，那攻击你的食肉动物会少之又少。
So getting big is the only game in town.
所以变大是唯一的生存手段。
A fully grown Sauroposeidon is 19 meters tall and almost 30 meters long.
一只成年波塞东龙能有十九米高，三十米长。
Its neck alone is four stories long, a single vertebra almost as tall as a grown man.
单单是脖子就有四层楼那么高，一根椎骨更是和成人身高相仿。
And a single thighbone weighs over half a ton.
一根股骨就有半吨重。
They seem to break all of the rules.
一切规则对它们都不适用。
There's nothing like them around today.
现今再也没有动物比得上它们。
Containing over 72 million calories of fresh meat,
它们的肌肉里含有七千二百万卡路里的热量，
you'd thlnk Sauroposeidon would be the jackpot for a bloodthirsty carnivore.
你一定会以为波塞东龙是血腥食肉动物的大餐了吧。
They don't have horns. They don't have armor.
它们没有角，也没有装甲。
Really, the only antipredator defense they have is sheer size. And size does matter.
唯一阻挡捕食者的防御就是它们的庞大体型。而体型确实很管用。