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Their teeth were recurved which means they start to point backwards and they were also very blade-like and had serrated edges.
它們的牙齒后彎曲，這意味著它們開始指向后方，它們也是很像利刃邊緣呈鋸齒狀。
Three tons of terror moving at 30 miles an hour would have been a stunning sight.
三噸重的恐怖猛獸以20英里的時(shí)速移動(dòng)，這可會(huì)是驚人的一幕。
What made them even more fearsome was that they hunted in packs.
讓它們更加可怕的是它們成群狩獵。
We've collected in fact 12 good skeletons in southern Alberta.
事實(shí)上我們在阿爾伯塔南部找到了十二具完整骨骸。
In addition to that, we have a bone bed that Barnum Brown worked in 1910 where we have parts of 23 skeletons of Albertosaurus.
除此之外，巴納姆·布朗1910年時(shí)考察過的骨床有部分二十三副阿爾伯特龍的骨骸
And these are everything from 2-year-olds to 25-year-olds.
這些從兩歲到二十五歲的都有。
As adults, as juveniles, or sub-adults or we called teenagers, all found together at the same time at the same place.
成年恐龍、幼年恐龍還有快成年的青年恐龍，都在同一時(shí)間同一地點(diǎn)被發(fā)現(xiàn)。
And this suggested that they may have operated in family groups,so they may not have nearly been very powerful predators, they may have be very powerful pack hunting predators.
這表明它們可能以家庭為單位進(jìn)行活動(dòng)，也許它們不是那么厲害的掠食者，但它們會(huì)是非常厲害的群體掠食者。
Fossils of varying sizes have been found very closely together pointing to the fact that Albertosaurus may have lived in family units.
尺寸不一的化石在相距甚近的地方被發(fā)現(xiàn)表明阿爾伯特龍有可能以家庭為單位活動(dòng)。
This would have increased the survival of their young and helped the Albertosaurus expend its territory.
這樣能增加它們幼崽的生存機(jī)會(huì)也能幫助阿爾伯特龍拓展勢力范圍。
But even these well-adapted dinosaurs were vulnerable to climate change.
不過即使這些適應(yīng)力很強(qiáng)的恐龍?jiān)跉夂蜃兓媲耙膊豢耙粨簟?/div>
In the late Cretaceous period, temperatures inexplicably began to climb.
在晚白堊紀(jì)時(shí)期氣溫莫名地又開始攀升。
A pretty dramatic change in the climate was becoming obvious at the end of the Cretaceous.
這一氣候上相當(dāng)劇烈的變化在白堊紀(jì)末期變得愈發(fā)明顯。
We find fossil evidence of cold-blooded animals and plants that don't really tolerate the cold that well being found in the polar regions.
我們在極地地區(qū)發(fā)現(xiàn)了一些不能忍受寒冷的冷血?jiǎng)游锖椭参锏幕C據(jù)。
Why the earth began to warm after the cooling period is still a mystery.
地球?yàn)槭裁丛诤鋾r(shí)期之后又開始變暖現(xiàn)在仍是個(gè)迷。
One interesting hypothesis involves the larger amounts of water that once covered much of the earth.
一種有趣的假說用曾經(jīng)大量覆蓋地球的水來解釋。
Rather than absorbed the heat, they may have radiated it back into the atmosphere and cause a green house effect.
它們不是吸收熱量，而是將其反射到空氣中形成溫室效應(yīng)。
Whatever the case, these changes were tough to deal with for some dinosaurs, especially those up north.
無論是為什么，這些變化對(duì)一些恐龍來說并不好對(duì)付，特別是在北面生活的那些。
As temperatures rose in the late Cretaceous period, lush foliage grew, supporting larger and larger herbivores.
隨著白堊紀(jì)晚期氣溫回升，茂盛的植物大量生長，供養(yǎng)著越來越大的植食動(dòng)物。
These giant plant eaters like Triceratops developed horns for protection.
這些像三角龍一樣的巨大的植食者進(jìn)化出角來進(jìn)行防御。
The meat eater also adapted.
食肉者也隨之而改變。
The result was a predator whose name instills fear even today.
結(jié)果是一種名字即使是今天也讓人膽寒的掠食者。
The king of the dinosaurs - Tyrannosaurus Rex.
恐龍之王，雷克斯暴龍。
Tyrannosaurus Rex is without a doubt the biggest and baddest predator that ever walked North America and quite possibly the world.
雷克斯暴龍毫無疑問是北美地區(qū)很可能是全世界出現(xiàn)過的最大最厲害的掠食者。
They first appeared during the late Cretaceous about 68 million years ago and lived right up to the extinction of the dinosaurs about 3 million years later.
它們最早出現(xiàn)于白堊紀(jì)晚期大約六千八百萬年前，一直生活到三百萬年之后恐龍滅絕的時(shí)候。
Their range included Montana, Wyoming, Colorado, New Mexico, South Dakota and Canada, and even as far south as Texas.
它們分布于蒙大拿州、懷俄明州、科羅拉多州、新墨西哥州、南達(dá)科他州和加拿大，甚至最南達(dá)到德克薩斯州。
T-Rex stood out as the largest predator.
霸王龍是出類拔萃的最大掠食者。
It weighed up to seven tons, stood nearly five meters tall, and measured thirteen meters in length.
重量可達(dá)七噸，站立高度近五米，長度為十三米。
