Agreeing with subjects in number: The rare split of Amuzgo verbal inflection

Verbs in San Pedro Amuzgo, an Oto Manguean language of Mexico, often have two different stems in the paradigm, one used with singular subjects and the other with plural subjects. This constitutes a split motivated by number which is typologically interesting due to its rarity, since number splits are commonly only associated with the S and the O arguments, but not S and A as subject. Apart from at stem level, the split is also manifested in the incompletive of an inflectional class of verbs. At stem level the plural stem is derived in a variety of unproductive ways, making the relation between a singular stem and plural stem, synchronically, one of suppletion. In this paper, we study the distribution and the morphological properties of this split in depth, using a sample of almost 600 fully inflected verbs from a large database compiled by native linguist Fermin Tapia and now publicly accessible online at http://www.oto manguean.surrey.ac.uk/ on the Surrey Morphology Group's website. We also place it in a typological context, relating it to other systems we have observed.