One of the traits which allowed dinosaurs to dominate the fauna of the jurassic and cretaceous periods was that they grew rapidly .
使恐龙成为侏罗纪和白垩纪的动物之王的其中一个特征是它们生长迅速。
Today we 've got an oxygen level of 21 percent , but we know the levels have varied greatly in the past 400 million years and have declined steadily since the middle of the cretaceous .
Different feathers have different patterns of colour , suggesting that cretaceous dinosaurs-flying or otherwise-used their feathers for display .
不同的羽毛有不同的颜色样式,这表明白垩纪时期的会飞恐龙和陆地恐龙都利用羽毛来炫示自己。
The mass extinction at the end of the cretaceous was caused by a collision between earth and an asteroid or comet .
在白垩纪末期由于地球与小行星或彗星相撞造成了一场大灭绝。
He says it took about 10 million years for lizards and snakes to recover anything like their cretaceous diversity .
他还表示蜥蜴和蛇又用了一千万年恢复到白垩纪时期的多样性。
As they write in naturwissenschaftenthis week , the researchers believe this plant-eating beast lived during the cretaceous period , which lasted until about 65 million years ago .
The top picture shows similar filaments discovered by dr mckellar and his team , suggesting flightless dinosaurs sporting such protofeathers were still around in the late cretaceous .
The researchers suggested that the climate might have been cooler when this feathered giant lived than it was when t. rex roamed in the late cretaceous period .
研究人员认为长羽毛的大家伙生活的气候可能比暴龙流浪的白垩纪晚期更凉爽。
The cretaceous equivalent of zebra and antelopes-the victim species in every wildlife documentary about the dramas of the african savannah-were herbivorous dinosaurs called ornithopods .
白垩纪被称为鸟脚亚目食草恐龙其地位相当于斑马和羚羊每部有关非洲大草原的纪录片中被捕杀的种群。
Having warm blood and a high metabolic rate may have contributed to the evolutionary success dinosaurs enjoyed for hundreds of millions of years throughout the triassic , jurassic and cretaceous periods .