[footnote:] For instance, if one reconstructs satəmization, the merger of *K and *Kʷ, as an innovation that defines a clade (approx. Thraco-Armeno-Daco-Albano-Balto-Slavo-Indo-Iranian), then the other remaining Indo-European branches must independently undergo centumization as they branch off at higher nodes. Each of these individually centumizing higher clades (Anatolian, Tocharian, Italo-Celtic, and Germanic) represents undesirable homoplastic innovations.
Source: wiktionary