In most Portuguese-related Creoles (PRCs) nouns and verbs are systematically distinguished by contrasting prosodic patterns, which are therefore part-of-speech (POS) sensitive. Because they proceed from Portuguese infinitives having discarded final /r/, verbs end in CV syllables in PRCs (except in Diu Indo-Portuguese). When suprasegmental dominance is realized as stress, verbs bear main stress on this final syllable, whereas CV-ending nouns are stressed on the penult. Only nouns ending in heavy (CVC) syllables show final stress. When tone is the main suprasegmental, different tone patterns distinguish nouns from verbs. PRCs thus depart from their lexifier where stress assignment is not POS-sensitive, and instantiate a rare typological feature: morphophonological devices exclusively devoted to tell POS apart. The present study attempts to account for this state of affairs. The starting point was variable final r-drop in sixteenth century Portuguese and Língua de Preto (LDP), the Basic Variety among African slaves in Portugal. In LDP and subsequent creoles, however, it only affected infinitives, thus leading to the stress/tone POS divide. I argue that the need to distinguish predicative from argumental items, especially pressing in unguided L2 learning situations, was the leading force behind a change that resulted in a major typological split.

Keywords: Basic Variety, infinitive, Língua de Preto, part of speech, rhotic, stress, suprasegmental, syllable structure, tone, unguided second language acquisition