subunguis

…covering a ventral plate (subunguis), the whole capping the bony tip of a digit. Nails—found only in mammals—consist of a broad and flattened unguis, with the subunguis reduced to a vestige under the outer tip. Hooves, the characteristic feature of the hoofed mammals, or ungulates, are exaggerated nails, with…

…somewhat softer plate, called the subunguis, covers the bottom of the toe and is extensively developed in hoofed animals to form a tough pad. (In humans the subunguis is only a small ridge under the tip of the nail.) Horseshoes are nailed to the hard unguis to protect the horse’s…