Phonological history of Spanish coronal fricatives

In Spanish dialectology, the realization of coronal fricatives is one of the most prominent features distinguishing various dialect regions. The main three realizations are the phonemic distinction between /θ/ and /s/ (distinción), the presence of only alveolar [s] (seseo), or, less commonly, the presence of only a denti-alveolar [s̟] that is similar to /θ/ (ceceo).