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The thing about extinction events is that, of course they're very bad for the animals that go extinct, but they open up a door of opportunity for a lot of other animals and plants.
其实就灭绝事件来说，当然对走向灭绝的动物来说很糟糕，不过这也为很多其它动物和植物，打开了机会之门。
And basically once certain species disappear, then other species will evolve and change and take over their place in that particular ecosystem or habitat.
基本上一旦某种物种消失了，其它物种就会进化，改变并取代它在特定生态环境或栖息地的位置。
Ultimately, it would be the giant asteroid that would end the reign of the dinosaurs.
最终，一颗巨大的小行星终结了恐龙的王朝。
But that deadly space missile would take another 250 million years to finally reach the earth.
不过那颗致命的太空导弹还要再花两亿五千万年才会到达地球。
In the meantime, the dinosaurs waged a savage battle for survival.
在此期间，恐龙发动了一场惨烈的生存之战。
144 million years ago, at the end of the Jurassic era, many dinosaur species became victims of climate changes that probably brought about their first extinction.
一亿四千四百万年前，在侏罗纪末期，很多恐龙种类成了气候变化的受害者，这大概带来了它们的首次灭绝。
But a host of others managed to rise to power.
不过其它一些恐龙设法登上统治地位。
More efficient plant eaters like Gastonia and Tenontosaurus were able to fill the void left by their predecessors, and in turn, new predators appeared along with them.
更多高效的植食者，比如加斯顿龙和腱龙，能够填补前辈留下的空缺，反过来，新的掠食者也就随之出现。
At the top of the food chain are the Raptors.
在食物链的顶端是迅猛龙。
These predators were more advanced than their earlier cousins.
这些掠食者比它们早期的亲戚更加先进。
This is when raptors, like Deinonychus and Utahraptor made their debut.
正是这个时候，迅猛龙，比如恐爪龙和犹他盗龙，初次登场。
Over the next 79 million years, dinosaurs continued as the unchallenged rulers.
接下来的七千九百万年，恐龙仍是不可动摇的统治者。
No other animals could match their size, power or ferocity.
没有其它动物能比得了它们的体型、力量或凶残。
By the end of the Cretaceous period, global environmental changes saw the emergence of tougher, more fibrous species of plants.
到了白垩纪末期，全球的环境变化带来了更坚韧、纤维更多的植物物种。
To take advantage of these new food sources, specially adapted herbivores evolved.
为了能够利用这些新的食物来源，进化出了特化的植食动物。
By the end of the Cretaceous, we had some very advanced dinosaurs.
到了白垩纪末期，出现了一些非常先进的恐龙。
There were lots of species of Ceratopsians, these were the horn dinosaurs.
有很多种角龙，这些是长角的恐龙。
And there were an abundance of duckbilled dinosaurs called Hadrosaurs.
还有很多嘴部像鸭喙的恐龙，称之为鸭嘴龙。
Both of these groups had remarkably advanced teeth and jaw design which allowed them to eat a wider variety of plants.
这两类恐龙都有相当先进的牙齿和颌部构造，使之能够吃更多种类的植物。
And the predators also had become more advanced.
掠食者也变得更加先进。
Dinosaurs like Albertosaurus was able to hunt cooperatively with other members of their own family, while raptors took pack hunting to a whole new level.
像阿尔伯特龙这样的恐龙与家族中的其它成员能够进行合作狩猎，而迅猛龙更是将群体猎食带到了全新高度。
But sitting atop all of these was Tyrannosaurus Rex.
不过首屈一指的是雷克斯暴龙。
He was the ultimate predator in earth's history.
它是地球历史中的终极掠食者。
And yet with all these evolutionary advancements, they literally disappeared in the blink of an eye.
但尽管有着所有这些进化优势，它们转瞬间就消失了。
65 million years ago, the giant asteroid that had been hurtling towards earth finally struck.
在六千五百万年前巨大的小行星经过飞向地球的漫长的岁月终于到达。
Nothing was safe.
没什么是安全的。
All the dinosaurs in the world at that time became extinct along with a lot of the big reptiles that sort of looked like dinosaurs, things like Mosasaurs and Plesiosaurs in the ocean,
那时全球所有的恐龙都走向灭绝，一起的还有很多看起来有点像恐龙的大型爬行动物，像是海洋里的沧龙和蛇颈龙，
and, on land of course the Tyrannosaurus Rex, and Nanotyrannus, and Triceratops, and all the duck-bill dinosaurs, and all the little raptors and so forth.
当然陆地上的霸王龙，矮暴龙，三角龙和所有的鸭嘴龙，还有所有的小迅猛龙等等。
It was a pretty much extinction of everything.
基本上所有的都灭绝了。
For many years, scientists were baffled by this massive extinction.
很多年来，科学家们为这次大灭绝而困惑。
It seemed incredible that so much carnage could have been caused by a single, sudden, catastrophic event.
似乎很难相信一次单独突发的灾难性事件能带来那么多的大屠杀。
The time in geological history that separates that end of the Cretaceous from the Tertiary Period is marked with a very distinctive band of clay.
在地质历史中分开白垩纪末期和第三纪的那段时间被记录在非常独特的一层黏土中。
You can see this thin band in locations throughout the world and it clearly marks the spot where something major had taken place.
在全球都能看到这薄薄的一层黏土，它非常清晰地标出发生过重大事件的地点。
Below it we find dinosaurs, pterosaurs and a variety of giant sea reptiles.
在这层黏土之下我们发现了恐龙、翼龙和各种大型海洋爬行动物。
But above that line, we don't see any evidence of these same creatures.
不过在那条线以上，我们没有看见过任何这些同种生物的证据。
So this layer clearly represents that something dramatic had happened on earth that caused a mass extinction in a very short time.
所以这一层黏土清晰地表明地球上曾发生过剧烈变化，并在很短时间内导致了大规模灭绝。
The layer that separates the periods is called the K-T boundary.
这区分两个纪元的土层被称作KT界限层。
