Stokes noticed several curved grooves preserved  alongside the tracks, and he believed these grooves were likely made by either that 4th  digit or the pteroid dragging along the ground.

斯托克斯注意到沿着轨道保留了几个弯曲的凹槽，他认为这些凹槽很可能是由第 4 指或沿着地面拖动的翼状体形成的。

You can see the kind of little bone that sticks out the front called the pteroid and that is used to move that front bit of wing up and down, which helps like the angle of attack.

你可以看到前面伸出来的一种小骨头叫做翼骨，它用来上下移动翅膀前面的部分，这有助于形成攻角。

And they also have a unique bone in their wrists  called the pteroid that would have supported the portion of the membrane between the wrist and  the shoulder, on the front edge of the wing.

他们的手腕上还有一块独特的骨头， 称为翼状骨， 它可以支撑手腕和肩膀之间的膜部分，位于机翼的前缘。