听力文本

These giant animals lumbered slowly across the landscape in large herds.
这些巨大的动物成群结队，在陆地上缓慢行走
With tiny brains the size of a golf ball,
它们的脑只有高尔夫球那么大
they were neither quick-witted nor fleet-footed. They didn't need to be.
所以它们既不聪明，也不灵敏，可是它们根本不需要这些
Sheer size was their defense.
庞大的体型是最好的防御武器
Only the youngest or the sickest were at risk from smaller predators.
只有老弱病残者才会面临较小的掠食恐龙的威胁
The reign of the long-necks lasted for 60 million years, and then they died out; no one knows why.
蜥脚类恐龙的统治持续了6000万年，接着它们就灭亡了，没有人知道原因

By the end of the final age of dinosaurs, the Cretaceous Period, things were very different.
到了恐龙时代的末期——白垩纪，情况变得很不一样
A new and more vicious species of dinosaur arrived on the scene, the massive carnivorous tyrannosaurs.
一种全新并且更为凶猛的恐龙登上了历史舞台，巨大的食肉霸王龙
They were enormous. They were the biggest carnivores known.
它们庞大无比，而且是已知最大的食肉动物
For the next 25 million years, these huge meat-eaters preyed upon everything around them.
在之后的2500万年里，这种巨型食肉恐龙捕食身边所有的动物
These giant predators never met the long-necked herbivores.
这些高大的掠食动物永远不会碰上植食蜥脚类恐龙
But there was a part of the world where evolution took a different path... South America.
但在地球上的某个地方，进化却走上了一条不同的道路。南美洲
Millions of years ago, when dinosaurs first appeared, all the land was connected in one huge super-continent, Pangea.
亿万年前，当恐龙刚开始出现时，所有的陆地板块都联结为一块超大陆--盘古大陆

词汇解析

1.at risk 处于危险中
Your child is at risk of getting one of these infections while waiting for the next injection.
你的孩子在等待下一次接种的时候，就会有感染这些传染病的危险。

2.last for 持续；延续
Then the strike will last for ever.
那么这场罢工会永远持续下去的。

3.arrive on the scene 露面；登场
Wyatt is about to shoot Mahone when police arrive on the scene.
怀亚特正想拔枪射向马宏时，警察到达了现场。

4.prey upon of 掠夺；捕食
Baboons most often form close bonds with relatives, the researchers said, and the stability of those connections is partly a matter of luck since lions and leopards often prey upon baboons.
研究者表示，狒狒通常会与亲属建立亲密的关系，不过由于狮子和豹子的捕食，使得这种关系的稳定性含有一定的运气成分。

视频及简介

BBC跟随着科学家到达阿根廷。在那里，他们挖掘到了一种崭新的恐龙。它们比暴龙还要大，是至今为止所发现的最大的食肉动物。这种捕猎者的头骨比一个人要大，上面还布满了锯齿状的，小刀样的牙齿和长的，强壮的颚肌肉。它们能够以外科手术般的精确度来把它们的猎物切成碎片。