Since the 19th century, scientists believed that cockroaches were an ancient group of insects that had a Devonian origin, according to one hypothesis.[13] Fossil roachoids that lived during that time differ from modern cockroaches in that they had long external ovipositors and are the ancestors of mantises, as well as modern cockroaches. As the body, hind wings and mouthparts are not preserved in fossils frequently, the relationship of these roachoids and modern cockroaches remains disputed.