But some also believe that a gamma ray burst was responsible for the Ordovician extinction around 455 million years ago.

但是也有一些科学家认为伽玛射线爆发可能是四十五亿年前奥陶纪大灭绝的罪魁祸首。

The Ordovician (440 million years ago) and Devonian (365 million) each wiped out about 80 to 85 percent of species.

奥陶纪（44000万年以前）和泥盆纪（36500万年以前）分别消灭了大约80%——85%的物种。

440 million years ago was the The Ordovician extinction.

4.4亿年前是奥陶纪大灭绝。

Before the Ordovician, terrestrial life was probably limited to microbes.

在奥陶纪之前，陆地生命 可能仅限于微生物。

By the time the Cambrian had segued into the Ordovician, cephalopods had entered a golden age.

当寒武纪进入奥陶纪时，头足类动物进入了黄金时代。

The Ordovician period also saw the advent of more active suspension feeders, like the giant, filter-feeding anomalocarid Aegirocassis.

奥陶纪时期还出现了更活跃的悬浮式捕食者，例如巨大的滤食性奇虾 Aegirocassis。

470 million years ago, in the Ordovician Period, the first plants began to live on land.

7亿年前，在奥陶纪， 第一批植物开始生活在陆地上。

The fossils they found were about 488 million years old -- which put them in the Ordovician.

他们发现的化石大约有 4.88 亿年的历史——这使它们处于奥陶纪。

And as the Ordovician progressed, cephalopods began to leave the shallows to explore the open ocean.

随着奥陶纪的进展，头足类动物开始离开浅滩探索开阔的海洋。

The Ordovician endoceratids cephalopods were the biggest animals of their time, reaching an impressive 6 meters in length.

奥陶纪的头足类动物是当时最大的动物，身长可达 6 米， 令人印象深刻。

Heading into the Ordovician Period, around 485 million years ago, eocrinoids diversified into thousands of forms.

进入大约 4.85 亿年前的奥陶纪时期，类分泌物多样化为数千种形式。

This fish lived in the coastal waters of what's now Bolivia, during the Ordovician Period, some 470 million years ago.

大约 4.7 亿年前的奥陶纪时期，这种鱼生活在现在玻利维亚的沿海水域。

These spores were dated to 462 million years ago - during that cooling event that took place in the Ordovician Period.

这些孢子可追溯到 4.62 亿年前——在奥陶纪发生的那次冷却事件期间。

Crinoids became the most abundant echinoderms of the Ordovician, and some were the ancestors of today's stalkless feather stars and stalked sea lilies.

海百合成为奥陶纪最丰富的棘皮动物，有些是今天无柄羽星和有柄海百合的祖先。

This twofold impact known as the Ordovician-Silurian Extinction, wiped out about 25% of all taxonomic families, including about half of trilobite families.

这种被称为奥陶纪-志留纪灭绝的双重影响消灭了大约 25% 的所有分类科，包括大约一半的三叶虫科。

The period right after the Cambrian is the Ordovician, and this is when paleontologists saw a major change in the composition of animal life.

紧接寒武纪之后的时期是奥陶纪，古生物学家正是在这个时期发现动物生命的构成发生重大变化。

And it might've been pressure to find a new feeding niche that drove this switch from face-up to face-down, since the Ordovician witnessed an explosion in suspension-feeding, with lots of competition for floating bits of food.

并且可能是寻找新的喂养生态位推动这种从面朝上到面朝下的转变的压力，因为奥陶纪见证了悬浮喂养的爆炸式增长，对漂浮的食物进行了激烈的竞争。