i am 99% sure that it is manmade.
Kinda hard to breed out traits like appendages in animals no matter how much you selectively breed.
I remember trying this theory where they cut the legs off a giraffe to see if its babies would share the legless genes of the parent and grow longer necks. Sadly no longer necked giraffes, just regular giraffes with regular legs.
The moral of that story is that If you would manage to breed 2 tailless angels, I am positive they would yield tailed babies. And if they did yield ALL tail-less babies then they are NOT man-made.