Shelly creatures such as trilobites and brachiopods, of whose ancestors there is little sign in the rocks, are suddenly everywhere.

像三叶虫、腕足动物此般壳类动物的祖先没有在岩层中留下什么痕迹，但它们的遗迹却突然间比比皆是。

Some creatures like trilobites and brachiopods survived though.

不过，一些生物如三叶虫和腕足动物幸存下来。

Yes, there were some mollusks and simple shelled creatures like brachiopods.

是的，有一些软体动物和简单的带壳生物，如腕足动物。

These tubes appeared only on brachiopods — never alone or on other animals.

这些管子只出现在腕足动物身上——从来没有单独出现过， 也没有出现在其他动物身上。

This suggests that the tube-dwelling creature needed the brachiopod to survive.

这表明这种管栖生物需要腕足动物才能生存。

Thousands of brachiopod fossils at the site had been clustered in sediment once covered by the sea.

该遗址的数千块腕足动物化石曾聚集在曾经被海水覆盖的沉积物中。

Plankton diversified, followed by a host of suspension feeders like certain types of brachiopods, rugose corals, and bryozoans.

浮游生物多样化，随后出现大量悬浮饲养者，如某些类型的腕足动物、皱纹珊瑚和苔藓虫。

The brachiopods were likely filter feeders.

腕足动物很可能是滤食动物。

If true, then tube-covered brachiopods would get less food.

如果属实，那么管状腕足动物将获得更少的食物。

Now, a fossil bed of brachiopods in Yunnan, China, offers strong evidence for parasites from almost 100 million years earlier.

现在，中国云南的腕足动物化石床为近 1 亿年前的寄生虫提供了强有力的证据。

And that means they should weigh less than brachiopods without the tube dwellers.

这意味着它们的重量应该比没有管住者的腕足动物轻。

To investigate, Zhang's group estimated the mass of brachiopods with and without tubes.

为了进行调查， 张的团队估计了带管和不带管的腕足动物的质量。

Brachiopods with more tubes should be worse off, he says.

他说，管子较多的腕足动物应该情况更糟。

While brachiopods with tubes were smaller, Leung says, this might not be due to parasitism.

梁说，虽然带管的腕足动物较小， 但这可能不是由于寄生。

Brachiopods hosting tube dwellers might become stressed only when food becomes scarce, for instance.

例如，只有当食物变得稀缺时， 居住在管内的腕足动物才会感到压力。

Or it could be that the tube dwellers catch food that would be too small for the brachiopods.

也可能是管内居民捕获的食物对于腕足动物来说太小了。

Zhang and his colleagues wondered if the tube-dwellers had been snatching food at the shell's edge, before the brachiopod could eat it.

张和他的同事们想知道， 在腕足动物吃掉食物之前， 管栖动物是否一直在抢夺壳边缘的食物。

One hundred million years later, the warm, shallow seas were packed with tiny plants and animals — essentially, hors d'oeuvres for a plethora of bigger creatures like trilobites, conodonts, brachiopods, and corals.

一千万年之后，温暖的浅海充满了微小的植物和动物——基本上是大量大型生物的开胃菜，如同三叶虫，牙形虫，腕足类和珊瑚。

Most of the main groups of the animal kingdom—arthropods, brachiopods, coelenterates, echinoderms, molluscs and even chordates, the branch from which vertebrates went on to develop—are found in the fossil beds of the Cambrian.

人们在寒武纪群落里发现了动物王国的主要动物集群，包括腕足、腔肠、棘皮、软体和脊索（脊椎动物进化的分支）。