I'm sure I've asked this before, but of what material are cephalopod beaks composed? I'm guessing keratin, or something similar, but is any metal used? (Thinking of the radulla of certain marine snails here)
so, obviously cuttlebones (presumably including spirula) and nautilus shells are calcium based... are squid pens and the vestigial shells of some octos also rather than chitin? How about statoliths? I know squid sucker rings are also chitinous. How about radulas? and yeah, I could probably look this stuff up if I wasn't lazy... Is it pretty much across-the-board that all cephs can make both calcium and chitin based hard bits?