"The parietal eye is found in the tuatara, most lizards, frogs, salamanders, certain bony fish, sharks, and lampreys...It is absent in mammals, but was present in their closest extinct relatives, the therapsids"
Wings are so fascinating. Flying animals have their whole body, from their brain, digestive system, down to their bones internal structure and function [0] optimized for flight. That's where we see species giving up flight ability to get a stronger body, and I wonder what it would take for us to do the reverse to be able to use these wings in any way.
We'd definitely have to give up long gestation and with that, live birth, and probably a good amount of cranial capacity due to weight and energy budget tradeoffs.
Bats do not have the cranial size of humans; that's kind of the point. They may have a loosely comparable cranium to body mass proportion, but allometric mass scaling matters with respect to physiological adaptation, quite a lot[0].
