Athematic participles in Brazilian Portuguese: A syncretism in the making

Some Portuguese verbs have two different past participles, such as, e.g., aceitar 'accept', with participles aceitado and aceito; and limpar 'clean', with limpado and limpo. The first one in each pair mentioned is thematic, whereas the second one is athematic. While regular thematic participles all bear stress on the theme vowel, these athematic participles all bear the primary stress on the athematic stem. As the morphosyntactic category first person singular present indicative (1spi) is realized by {-o}, it normally coincides the masculine form of this athematic participle, giving rise to a syncretism between 1spi and the participle. The aim of this paper is to track the appearance of this kind of participle and the resulting syncretism in Portuguese and the changes making it possible for new participles to be formed in this way in colloquial Brazilian Portuguese.