 Paleontologists believe that the males of the ancestral placoderm had pelvic claspers, but the claspers were lost in the evolutionary development of each of the placoderm orders, save for the ptyctodontids (there are too few whole specimens of the primitive "Stensioella heintzi" to tell if the males of that species had claspers or not).Because they had reduced armor, the ptyctodontids were once thought to be the most primitive of the placoderms.Indeed, there has been the idea that the placoderms had a gradient, of sorts, from the least armored, and most primitive forms, to the heavily armored, most advanced forms.