Automotive vehicle seat with backrest hinge covering

The seat has backrests contiguous to a seat base and mounted on an articulation carried by a structure unit. The articulation permits independent rotation of each part of the backrests. The articulation has a fitting (10) formed of a flexible arched prong (11) that is carried by a case. The case that closes an opening realized by the articulation on a rear part of the backrests has a cavity (19) to store a seat manipulation strap.