Iranian languages:

It is possible that other distinct dialect groups were already in existence during this period. Good candidates are the hypothethical ancestor languages of Alanian/Scytho-Sarmatian subgroup of Scythian in the far northwest; and the hypothetical "Old Parthian" (the Old Iranian ancestor of Parthian) in the near northwest, where original *dw > *b (paralleling the development of *ćw).

Please answer a question about this article. If the question is unanswerable, say "unanswerable". What possible predecessor of Pathian is thought to have existed?
Old Parthian