The blank could be filled in with humerus since it is the longest bone in the leg.
I'm pretty sure that sea horses can too
Nucleus would be your answer
I think the most critical consequence of the advancement of the amniotic egg it the tetrapods were no longer attached to the water for reproduction.The amniotic egg permits reptiles, flying creatures, and warm-blooded creatures to lay eggs ashore without drying out. The liquid filled depression containing the incipient organism is isolated from the outer condition by an amniotic sac that is impermeable to water.
