ɐ dˌɛfɪnˈɪʃən fɔːɹ ɪŋklˈuːʒən ɪnðɪ ˈɔːɹdɚɹ ɪz dˈɪfɪkəlt: ɪɾ ɪz ˈɔːlmoʊst ˈiːziɚ tə lˈɪst ðə pɹˈɪmᵻtˌɪvlidˈaɪəpsˌɪd ɹˈɛptaɪlz ðæt hɐvnˌɑːt bˌɪn ɪŋklˈuːdᵻd æt wˈʌn tˈaɪm ɔːɹ ɐnˈʌðɚ.
A definition for inclusion in the order is difficult: it is almost easier to list the primitively-diapsid reptiles that have not been included at one time or another.