At the border between Gallo-Romance and Italo-Romance, the dialects spoken in Menton as well as in the Roya and Nervia Valleys share distinctive systemic traits – morphophonological, in particular – that are absent in the neighboring varieties (Niçard, Costal Ligurian, Piedmontese). Based on a broad empirical dataset, the study isolates these archaic – and nowadays unique – Gallo-Italic traits, showing their clear affinity with Proto-Ligurian.