Relations within the Iranian branch of Indo-European have traditionally been modelled by a tree that is essentially composed of binary splits into sub- and sub-subbranches. The first part of this article will argue against this tree and show that it is rendered outdated by new data that have come to light from contemporary and ancient languages. The tree was also methodologically problematic from the outset, both for reasons of the isoglosses on which it is based, and for not taking into account distinctions such as shared innovations vs. shared archaisms. The second part of the paper will present an attempt at an alternative tree for Iranian by proposing a subbranch which I will call “Central Iranian”. Such a branch seems to be suggested by a set of non-trivial morphological innovations shared by Bactrian, Parthian and some neighbouring languages. The reconstruction of the nominal system of Central Iranian which will then be proposed aims to show the result one arrives at when trying to reconstruct a subbranch as strictly bottom-up as possible, i. e. using only the data from the languages under study, and avoiding profitting from Old Iranian data and from our knowledge about the proto-languages.