Oyster-bioimmured ammonites from the Upper Albian of Annopol, Poland: stratigraphic and palaeobiogeographic implications

Ammonites Mortoniceras (Subschloenbachia) sp. are preserved as attachment scars on the oyster shells from the topmost portion of the Albian succession at Annopol, Poland. These oyster-bioimmured ammonites show a closest affinity to the representatives offiloilonicei.ris (Subschloenbachia) characteristic of the upper Upper Albian perinflatum zone. No ammonites indicative of the uppermost Albian lowermost Cenomanian Pracschlocnbachia briacensis Zone are recorded. Thus, the hiatus at the Albian Cenomanian boundary at Annopol embraces the latter zone. The presence (and dominance) of Mortonicerris in the upper Upper Albian ammonite assemblage ofAnnopol suggests that the representatives of this Tethyan genus could migrate into the epicratonic areas of Poland directly from the Tethyan Realm, pia the Lwow (Lviv) region.