ɪn wˈʌn pɚtˈɪkjʊlɚ bɹˈæntʃ ʌvðə fˈæmɪli tɹˈiː, ðə ʃˈɛl ʌv kəntʃˈɪfɚɹənz ɪz θˈɔːt tə hæv ɪvˈɑːlvd fɹʌmðə spˈɪkjuːlz smˈɔːl spˈaɪnz ʌv ɐplˈækəfˌoːɹənz; bˌʌt ðɪs ɪz dˈɪfɪkəlt tə ɹˈɛkənsˌaɪl wɪððɪ ˌɛmbɹɪəlˈɑːdʒɪkəl ˈɔːɹɪdʒˌɪnz ʌv spˈɪkjuːlz.
In one particular branch of the family tree, the shell of conchiferans is thought to have evolved from the spicules (small spines) of aplacophorans; but this is difficult to reconcile with the embryological origins of spicules.