Patterns of the evolution of aptychi of Middle Jurassic to Early Cretaceous Boreal ammonites

摘要: Here we are providing a review of aptychi records in ammonites Boreal origin or that inhabited Boreal/Subboreal basins during the Bathonian–Albian with special focus on new and relationship between evolution ammonite conch aptychi. For first time figure belong to Aulacostephanidae, Virgatitidae, Deshayesitidae, Craspeditinae Laugeitinae. A strong difference micro- macroconchs co-occurring Aspidoceratidae is shown, which, along their shell morphologies suggests niche divergence these dimorphs. Aptychi Aptian Sinzovia (Aconeceratidae) should be tentatively ascribed Didayilamellaptychus, while previous assignment rhynchaptychi was caused by misidentification. Middle Jurassic–Early Cretaceous Subboreal characterized very thin calcareous non-porous outer layer lacking distinct ribs tubercles (only radial striae sometimes occur), mainly assigned Praestriaptychus. Some ammonoid groups (i.e. Ancylocerina Desmoceratoidea) presence different types irrespective shape. This fact could indicate bivalved praestriaptychi have easily transformed into single-valved “anaptychi” vice versa. Size form relation those aperture conchs vary within lineages at least some Stephanoceratoidea Perisphinctoidea significantly smaller than diameter.