vˌɑːlbɔːɹθˈɛlə, sˌʌm fˈɑːsəlz ʌvwˈɪtʃ pɹɪdˈeɪt , wʌz lˈɔŋ θˈɔːt təbi ɐ sˈɛfɐləpˌɑːd, bˌʌt dɪskˈʌvɚɹiz ʌv mˈoːɹ diːtˈeɪld fˈɑːsəlz ʃˈoʊd ɪts ʃˈɛl wʌz nˌɑːt sᵻkɹˈiːɾᵻd, bˌʌt bˈɪlt fɹʌm ɡɹˈeɪnz ʌvðə mˈɪnɚɹəl sˈɪlɪkən daɪˈɑːksaɪd sˈɪlɪkə, ænd ɪt wʌz nˌɑːt dᵻvˈaɪdᵻd ˌɪntʊ ɐ sˈɪɹiz ʌv kəmpˈɑːɹtmənts baɪ sˈɛptə æz ðoʊz ʌv fˈɑːsəl ʃˈɛld sˈɛfɐləpˌɑːdz ænd ðə lˈɪvɪŋ nˈɔːɾɪləs ɑːɹ.
Volborthella, some fossils of which predate , was long thought to be a cephalopod, but discoveries of more detailed fossils showed its shell was not secreted, but built from grains of the mineral silicon dioxide (silica), and it was not divided into a series of compartments by septa as those of fossil shelled cephalopods and the living Nautilus are.