The chronostratigraphic subdivision into an Early and Late Cretaceous is preceded by a global turnover in marine faunas, called the middle-late Albian Boundary Bio-Event. Thus, the late Albian is a critical time interval, especially with respect to the evolution and radiation of ammonites, which are sections). This led to the construction of a sequence of 23 UAs for the whole late Albian, which represents a higher resolution than the standard empirical interval-based zonations for northwestern and southwestern Europe (7 zones and 9 subzones, respectively). These UAs can also be merged into 9 more geographically reproducible association zones, which correlate very well with the two standard zonations. Based on our results, the UAM enables accounting for and highlighting the range of actually all taxa, and not just a few selected index taxa whose ranges very often extend before and/or after their eponymous interval zone. Finally, the UA quantitative biochronology enables us to measure western European ammonite diversity throughout the whole Albian in detail. Consequently, we identified a major and sharp diversity decrease during the uppermost Albian (UAZ 8/9 boundary; = M. perinflatum/A. briacensis zones boundary), concomitant with the well-known Oceanic Anoxic Event OAE1d.