Al Feldstein, who took over a fledgling humor magazine called Mad in 1956 and made it a popular, profitable and enduring wellspring of American satire, died on Tuesday at his ranch in Paradise Valley, Mont. He was 88. His wife, the former Michelle Key, confirmed the death. In recent years, he was a wildlife and landscape painter in Montana, outside Livingston. Mr. Feldstein had been a writer and illustrator of comic books when he became editor of Mad four years into its life and just a year after it had graduated from comic-book form to a full-fledged magazine.