Whereas Marcel Cohen (1947) claimed he saw no evidence for internal subgroupings, numerous other scholars have made proposals, with Carsten Peust counting 27 as of 2012.
wˈɛɹæz mɑːɹsˈɛl kˈoʊən nˈaɪntiːnhˈʌndɹɪd fˈoːɹɾi sˈɛvən klˈeɪmd hiː sˈɔː nˈoʊ ˈɛvɪdəns fɔːɹ ɪntˈɜːnəl sˈʌbɡɹuːpɪŋz, nˈuːmɚɹəs ˈʌðɚ skˈɑːlɚz hæv mˌeɪd pɹəpˈoʊzəlz, wɪð kˈɑːɹsʔn̩ pjˈuːst kˈaʊntɪŋ twˈɛnti sˈɛvən æz ʌv tˈuː θˈaʊzənd twˈɛlv.