Allosaurus was really the first of the truly big meat-eating dinosaurs that was found and was the one from fairly complete remains.

异特龙真的是被发现的第一种大型肉食恐龙而且其骨骼保存相当完整。

It was the Tyrannosaurus-Rex before there was a Tyrannosaurus-Rex, both in terms of geological time and its discovery.

它是霸王龙之前的霸王龙，从地质时间和被发现的时间上都是如此。

Powerfully muscled, Allosaurus was able to hunt huge herbivores, like the two-ton stegosaurus.

异特龙肌肉发达，能够捕猎大型植食动物，比如重达两吨的剑龙。

Allosaurus in its time was the top predator.It was a combination of a lot of really useful traits for a predator.

异特龙是那一时期的顶级掠食者。它身上集合了很多掠食者非常有用的特征。

It had powerful jaws with pretty sharp teeth.

它的双颌有力还有很锋利的牙齿。

It had large claws on its hand which are very useful for gripping and tearing.

它的前肢上有巨大的爪子，在握紧和撕扯时很有用。

So it combined a lot of useful traits as a hunter.

所以作为一个猎手它结合了很多有用的特征。

Allosaurus has got relative long arms for a big predatory dinosaur.

异特龙在大型掠食恐龙里前肢是比较长的。

Most predators have these little arms and they are not very effective weapons.

多数掠食者前肢短小而且它们不是非常有效的武器。

But Allosaurus is different. He's got three enormous claws on each hand.

不过异特龙并不一样。它的每个前肢上有三个巨大的爪。

And listen, you don't have the big claws to play the piano.

注意，长出大爪子可不是要弹钢琴。

You have big claws to rip somebody's head off.

有大爪子是要把别人的脑袋扯下来。

I think another way to look at Allosaurus is if you were to take a wolf and make it into a two-ton animal, put on two legs, put Edward-Scissorhands-like arms on it with giant claws, and then maybe put a skull of an alligator on top of that carnivorous animal.

我觉另一种看特异龙的方法，就是把一头狼放大变成两吨重，让它两足行走，换上剪刀手爱德华那样的带长爪的前肢之后，再把短吻鳄的脑袋给这个肉食猛兽安上。

Allosaurus was a fast, strong, ferocious beast.

异特龙是一个迅速、强壮、凶猛的野兽。

It stood about 3 meters tall, measured nearly 12 meters in length, and weighed up to 4 tons, making Allosaurus one of the biggest meat eaters of its time.

它站起来有三米高，长度接近十二米，重可达四吨，这使得异特龙成为那一时期最大的肉食者之一。

The reason why Allosaurus and other dinosaurs were able to grow so big is because the oxygen levels were much higher back then than they are today.

异特龙和其它恐龙能长到如此巨大，是因为那时的氧气水平比现在高得多。

And so dinosaurs were able to extract oxygen without much effort, and therefore they could carry a heavier load and live more active lives even though they were huge.

所以恐龙不用费力就能获得氧气，因此它们能挑更重的担也能活得更活跃，即使它们是巨大的。

During the late Jurassic period, oxygen levels have been estimated to be as high as 35 percent, higher than our current 21 percent oxygen level, making life much easier for the large dinosaurs.

在侏罗纪时晚期，氧气水平据估计高达35%，比我们现在的21%高，这使得大型恐龙的生活容易得多。

So how on earth could anyone know what the oxygen level was a million years ago?

那么我们到底是怎么知道一百万年以前氧气水平有多高呢?