This list of language groups seems to represent a general view shared by linguists as to the availability of written texts. However, there are some languages that have not received the attention they deserve and the Iranian, or the Irano-Aryan sub-branch of the Indo-Iranian languages is one of them. Although they were always behind the more conspicuous Indo-Aryan group, languages belonging to this group have historical documentation covering no less than 3,000 years, and numerous different modern languages of this group are spoken in the vast area extending from Anatolia to China's western border. Thus, the Iranian languages have a lot to offer for diachronic studies, no less than Italic or other Indo-Aryan branches. I will present selected topics from Iranian historical linguistics, in particular the Eastern Middle Iranian dialects of the Pre-Islamic period, and discuss how they relate to the tree model.