This paper describes and analyzes data from a number of Modern Iranian dialects spoken in Khorasan in the east of Iran which are unusual among the other Western Iranian languages in that they have grammaticalized a split tense-sensitive alignment in indexation, compared to other Iranian languages whose indexation splitness is sensitive to both tense and transitivity. These dialects are the former dialect of Birjand in the late nineteenth and early twentieth century, the present-day dialect of Ferdows, Khanik, and Se-Ghal’e. The findings are put in the context of the available data from the Classical Persian texts to show that the tense-sensitive splitness mentioned above is traceable in those texts. A number of external factors are discussed which seem to have been influential in the restructuring of the split-alignment of the former dialect of Birjand into a uniformly nominative-accusative alignment in terms of indexation as observed in the present-day dialect of Birjand. It is proposed that this restructuring is an instance of simplification. The three other dialects cited above are endangered in the sense that they can undergo the same kind of restructuring as happened to the dialect of Birjand.
