ɡˈʊd ˈɛvɪdəns ɛɡzˈɪsts fɚðɪ ɐpˈɪɹəns ʌv ɡˈæstɹəpˌɑːdz, sˈɛfɐləpˌɑːdz ænd baɪvˈælvz ɪnðə kˈæmbɹiən pˈiəɹɪəd .
Good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period .