Non-past and past verb stems in Tangut

Over the past decade, the documentation of Gyalrongic languages has shed light on grammatical phenomena which were poorly understood in Tangut, a language of critical importance in the field of Sino-Tibetan comparative linguistics. This paper provides an explanation for the last remaining unelucidated verbal alternation in Tangut (-i(1)/-i(2)), which, as I will demonstrate, encodes a non-past/past distinction. By doing so, it also gives fresh arguments for placing Tangut and the Horpa languages together within one clade. Finally, methodologically speaking, it offers an example of grammatical reconstruction from above, i.e. employing sister languages to better understand the grammar of an extinct language through their common ancestor, revealing a rare example of complex distributional retention uncorrelated with regular phonetic correspondences.