Don’t gotta be a mammal to qualify for a belly button. A chick is attached to the yolk sac while it’s growing inside it’s shell. That’s how they get nourishment to grow. When they hatch, there’s a small scar where the cord from the yolk sac had been attached.
Don’t gotta be a mammal to qualify for a belly button. A chick is attached to the yolk sac while it’s growing inside it’s shell. That’s how they get nourishment to grow. When they hatch, there’s a small scar where the cord from the yolk sac had been attached.