One of my favorite childhood TV shows was 'BATMAN'... so many fond memories!! ... sad to hear of Adam West's passing.... Here is a tribute to one of my childhood heros. RIP sir.
It's an embryonic issue, the disc doesn't fully connect in the front. All ray embryos start out this way, rarely some don't develop properly and you end up with a "batman" ray.
I am very sad to here about Adam...a lot of people don't know he was an extremely funny guy too. Great sense of humor! Will be missed.