The reasons why animals like Sauroposeidon have an enlargement in their hip
像波塞东龙这种动物之所以臀部有一部分扩张，
is because there's actually a lot going on back there.
是因为尾部的活动很多。
There are lots of muscles that are in the legs, and also muscles that are going through the tail.
腿部有很多肌肉，尾巴上也有很多肌肉。
The primitive brain the spinal keeps Sauroposeidon's legs and tail in sync with his body.
原始脑脊髓可以协调波塞东龙腿部和尾部的活动
Without it, they couldn't never have fed over such large territories, or possibly, they wouldn't even been able to walk at all.
没有第二个大脑，它们恐怕难以填饱肚子，甚至可能走路都成问题。
This tiny bundle of nerves weighing just few grams,
这样小小的神经组尽管只有几克重，
allows herds of Sauroposeidon to rule the great plains of southern Midwest of America for almost 50 million years.
却让波塞东龙种群在中西部南方的土地上统治了近五千万年。
Another plant eater couldn't appear more different. It's small, weak, and highly intelligent.
另一种食草动物却截然不同。它们身体弱小但非常聪明。

But like Sauroposeidon, Parasaurolophus live in herds.
但同波塞东龙一样，副栉龙也是群居动物。
They stick together and are constantly on the lookout for threats.
它们聚集在一起所以能够时刻保持警惕。
But for Parasaurolophus, there's a problem.
但对副栉龙来说有一个问题。
Their eyes are on the side of their head, so fields of view don't overlap.
它们眼睛长在头的两侧两眼，视觉范围不能重叠。
This leaves a blind spot dead ahead-a possible opening for an attacker.
这就造成了一个盲区——一个捕食者的可乘之机。
They couldn't see directly behind themselves, and they actually would have problems seeing directly in front of themselves.
它们看不到正后方，并且直视正前方也有些困难。
It's almost a different visual world than one that we can imagine.
这是我们很难想象的一种独特视角。
The Parasaurolophus have a solution to this problem.
对于这个问题，副栉龙自有解决办法。
When you've got multiple Parasaurolophus living together, that means multiple eyes to scan the horizon.
当有许多副栉龙群居在一起时，意味着许多双眼睛扫视周围。
And if one of you is feeding, munching on the plants on the ground,
当其中一个在吃草，俯在地面上大块朵颐时，
the other can keep its eyes out, looking around, keeping an eye out for Tyrannosaur.
其它的会保持警惕，四处张望提防霸王龙来袭。