The evolutionary past of starfishes from bilateral to radial animals is also echoed in their development.

海侧对称到辐射对称进化历史也反映在其发育过程中。

If you're just going to sit still, capture food, and not move around, the radial body plan may help you better access food in 360 degrees.

如果你只是静止不动， 捕获食物，不四处移动， 那么辐射对称身体构可能帮助你更好地在360度范围内获取食物。

So, as odd as the starfish body plan seems, something about it was successful -- from their ancient bilateral ancestors, to the radial crinoids with their upward-facing arms, to the predatory, downward-facing starfish.

所以， 尽管海身体构看起来很奇怪，但这种构显然是成功——它们古侧对称祖先，到向上伸出触手辐射对称早期海百合，再到向下捕食海。

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

已知最早具有辐射对称棘皮动物化石是弯脊动物，它出现在大约5亿1600万到5亿1300万年前宾夕法尼亚州。

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

左侧发育成五个部分，而右侧被吸收，最终形成一个成年辐射对称棘皮动物。