A horse has 5 toes, and then it doesn’t
New York Times article • February 8, 2020
The missing toes had in fact never left the horse, Dr. Kavanagh, Scott Bailey and [UCLA’s] Karen Sears report in a paper published Wednesday in the Proceedings of the Royal Society B. The finding suggests that certain stages of development cannot be changed, even if, in the adult animal, they leave no visible trace.