Shadow had/has (sorry i sold him so not sure whether to talk in present or past tense lol) one on his neck, they are found as a dent in the horse's body, often occuring on the neck or chest. It is said that Mohammed once tested his Arabian horses by depriving them of water for several days. He then let them all free near a watering hole, and they rushed to drink. Before they reached the water, he sounded his trumpet to call them, and only 5 mares returned. These 5 loyal mares were cherished and kept for breeding, the only ones fit to pass on their bloodlines. It is said that he pressed his thumb into their necks, marking them. Horses with thumbprints are thought to be good horses.
sweet story my arab mare has one under her mane and it's lovely to see,i've only known a few out of a hundred arabs to have it and i also know that her dam had one