since sammarinese is clearly an elision

Technically, in linguistics this is called assimilation (you can see it happening in Latin, where ad-similare became as-similare). It's opposite is dissimilation: e.g., L. arbor 'tree' to Spanish arbol. Both phenomena can happen to sounds in close proximity or sepearted by other sounds.

Elision is leaving out an initial or final sound. It happens in French, where some sounds that are silent at the ends of words are pronounced if the next word in the phrase/sentence begins with a vowel. Then there's Sanskrit's sandhi (pronounced almost like Sunday), where all kinds of changes happen to sounds at word boundaries.