Wiktionary:About Proto-Gallo-Romance

Proto-Gallo-Romance is the reconstructed ancestor of French (including other langues d'oïl), Franco-Provençal, Occitan, Gascon, and somewhat controversially Catalan, which may have been a transitional dialect. Its real-world counterpart would have been the Romance spoken in France and environs around the Merovingian period.

One of its characteristic features is its loss of final unstressed vowels except when needed to support consonant clusters (see here for examples).

For a reconstruction to qualify as Proto-Gallo-Romance, its reflexes should be attested in Old French by ca. AD 1150 as well as in at least two of the following: Old Franco-Provençal, Old Occitan/Gascon, Old Catalan. (There should be no clear reason to dismiss the forms in question as borrowings.) Failing this, there should be compelling phonological reasons to assign the reconstruction to Proto-Gallo-Romance.