Instead of curving downwards to make a regular rib cage, the ribs move outwards towards the carapacial ridge.

肋骨没有向下弯曲长成正常胸廓，而是沿着甲脊方向向外长。

At first, turtle embryos look very similar to those of other reptiles, birds, and mammals, except for a bulge of cells called the carapacial ridge.

起初，海龟胚胎看上去与其它爬行动物、鸟类和哺乳动物十分相似，除了一部分叫做甲脊的细胞。