Their cartilaginous skeletons are less dense than bony ones and require less energy to move.

这些生理特质从4亿多年中进化而来它们软骨质的骨架比硬骨的骨架更轻。

If we look at the really successful features of sharks you've got to consider this cartilaginous skeleton – that's no bone in the skeleton.

如果我们研究鲨鱼真正成功的特征，你必须要考虑到软骨骨架——那是指骨架中没有骨头。

Once contracted, they compress the arms of the cartilaginous skeleton at the base of the salamander's tongue, which then launches out with the rest of its tongue tissues.

一旦收缩，它们就会压缩蝾螈舌头底部的软骨骨骼，然后连同舌头的其他组织一起发射出来。