He says animals like sponges are even more ancient, but they lack the bilateral symmetry that characterizes most animals today.

他表示，海绵等动物更古老，但它们缺少现今大多数动物的两侧对称特性。

The scans confirmed the animals' bilateral body morphology and revealed the shape of the burrows they left from scavenging the seafloor.

描确认了这些动物的两侧对称身体形态，并揭示了它们在海底觅食时留下的洞穴形状。

To settle the debate researchers mapped gene expression in different bits of starfish anatomy, looking specifically for the genes expressed in the forebrain, midbrain and trunk of other bilaterians.

为了解决这个争论， 研究员绘制了海星解剖结构不同部位的基因表达图，专门寻找在其他两侧对称动物的前脑、中脑和躯干中表达的基因。