It is really highly frustrating how little we actually know about ammonites, despite the fact they are among the most abundant (non-micro) fossils. There are fantastic fossils with soft tissue impressions of belemnites, but there is nothing comparable from ammonites even from the same strata. Some of the ammonites are fossilized in really perfect condition, the only thing missing are soft tissue impressions. But even this absence of structures, gives us some clues. We can for example be quite sure that ammonites had no chitinous hooks like those of belemnites, as they fossilize comparably easy. It´s also not that probably that there were any suckers with chitinous parts. So there remains suckers, cilia or a surface similar to nautilus tentacles. I am still not completely sure how I will sculpt them. I don´t really like sucker-idea, at most I could imagine tiny sucker pads as those of Spirula. Vampyroteuthis-like cilia would be also a good choice I think. There is also not the slightest indicatpion of a beak in nautiloids, even in the best preserved fossils no chitinous beak is present, despite the fact that beaks are known from many other cephalopods like belemnites, nautilus and "modern" squids. Many reconstructions show nautiloids with beaks, even my own old models, but I won´t sculpt a beak in the newer models. There are several indications that ammonites were planctivorous, or at least mainly predators of very small prey. For this reason I will give them also a big "umbrella" between its tentacles, similar to those of Vampyroteuthis. As a planctivore doesn´t need super-strong senses, I will also sculpt the eyes comparably small.
And last but not least I still don´t know what to do with this stupid Aptychus!