“…Furthermore, the correlation of ammonites in Russian Tithonian and Berriasian boreal sections with a standard Mediterranean ammonite scale (SMAS sensu Reboulet et al, 2018) remains an intractable problem (e.g., Sazonova, 1971Sazonova, , 1972Sazonova, , 1977Casey, 1973;Casey et al, 1988;Mitta, 2005Mitta, , 2017Zakharov and Rogov, 2008;Schnabl et al, 2015). This is not only due to condensation and erosional episodes in the Russian platform 'Ryazanian' deposits (see Mesezhnikov et al, 1979;Mitta, 2014), but also the strong endemism of the ammonite faunas (e.g., Casey et al, 1977;Baraboshkin, 1999Baraboshkin, , 2002Mitta, 2004Mitta, , 2005; Zakharov and Rogov, 2008;Lehmann et al, 2015). Mitta (2017) has recently suggested that the type 'Ryazanian' beds of central European Russia can be separated into four zones.…”