And Camptostroma was paving the way for the echinoderms we see today.

Camptostroma 为我们今天看到的棘皮铺平了道路。

This researchers say that this finding is likely to apply to other echinoderms as well.

研究人员表示，这一发现也可能适用于其他棘皮。

It had the five-part symmetry common to all modern echinoderms.

具有所有现代棘皮共有的五部分对称性。

Echinoderms were hit hard and whole groups went extinct.

棘皮受到重创，整个群体都灭绝了。

Either way, the Paleozoic Era continued to be dominated by the crinoids and other echinoderms.

无论哪种方式，古代继续由海百合和其他棘皮统治。

Paleontologists also now have more information to go back and study the many strange fossils of echinoderms and their relatives.

古学家现在也有了更多的信息，可以回去研究许多奇怪的棘皮及其近亲化石。

All modern echinoderms start their lives as swimming larvae with bilateral symmetry and then settle on a substrate to transform.

所有现代棘皮都以双侧对称的游泳幼虫开始们的活，然后定居在基质上进行转化。

This makes Ctenoimbricata one of the first for-sure echinoderms.

这使得 Ctenoimbricata 成为首批确定的棘皮之一。

But why did some echinoderms become radially symmetric and develop this new body plan in the first place?

但是，为什么一些棘皮首先会变得呈放射状对称并发展出这种新的身体结构呢？

The left side grows into five parts, while the right side gets absorbed, and we end up with an adult radial echinoderm.

左侧长成五个部分，而右侧被吸收，我们最终得到了成年桡骨棘皮。

And yet the first echinoderms had no arms - not just Ctenoimbricata, but other species from the Cambrian Period, too.

然而， 第一批棘皮没有手臂——不仅是棘皮，寒武纪的其他种也是如此。

But today's adult echinoderms all share another special characteristic.

但是今天的成年棘皮都有另一个特点。

The story of echinoderms might actually go back a little further than Ctenoimbricata, to a 555 million year old fossil found in Australia.

棘皮的故事实际上可能比棘皮更早一点，可以追溯到在澳大利亚发现的 5.55 亿年前的化石。

Today, starfishes and brittle stars are the most successful groups of echinoderms in terms of abundance, diversity, and geographic distribution.

今天，就数量、多样性和地理分布而言，海星和海蛇尾是最成功的棘皮类群。

Well, there's a fossil gap between the early stalked echinoderms and forms that look like today's starfish.

好吧，早期有柄棘皮和今天的海星一样的形式之间存在化石间隙。

And it’s an important piece of the puzzle when it comes to understanding bilaterean evolution and figuring out how strange creatures like echinoderms relate to creatures like us.

当涉及到理解双边进化和弄清楚像棘皮这样的奇怪与我们这样的之间的关系时，这是一个重要的拼图。

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，有些是今天无柄羽星和有柄海百合的祖先。

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王国的主要集群，包括腕足、腔肠、棘皮、软体和脊索（脊椎进化的分支）。

The first radially symmetrical echinoderm known from the fossil record is Camptostroma, which showed up between 516 and 513 million years ago in Pennsylvania.

化石记录中已知的第一个径向对称棘皮是 Camptostroma，出现在 516 到 5.13 亿年前的宾夕法尼亚州。

Beginning about 240 million years ago, and continuing through the Late Triassic and Jurassic, starfishes diversified rapidly to become among the most common echinoderms, second only to the brittle stars.

从大约 2.4 亿年前开始，一直持续到晚三叠世和侏罗世，海星迅速多样化， 成为最常见的棘皮之一，仅次于海星。