In a closure assembly the cap is a quarter-turn cap and the bottom end of the skirt has a pair of diametrically opposed static cover portions separated from one another by a pair of diametrically opposed and open bottomed notches in the skirt. In each notch an indicator segment of the tamper-evident structure is located that is integrally molded to an upper notch rim by a non-frangible hinge, preferably a film hinge, and to each of the leading rim and the trailing rim via at least one respective frangible bridge. The neck has for each indicator segment an integrally molded boss adapted to engage on a respective indicator segment such that, upon first time opening of the cap by quarter turn rotation in opening direction, the indicator segments are each forced outwardly by the respective boss such that each of the indicator segments pivots about the non-frangible hinge and the frangible bridges break, thereby the outwardly pivoted indicator segments and the broken frangible bridges evidencing the first time opening of the cap.