Phylogeny of the ammonite family Aulacostephanidae Spath, 1924 during the Late Oxfordian and the Early Kimmeridgian in Europe: Main lineages, patterns of evolution and sedimentological to palaeogeographical controls on evolutionary development

The evolutionary history of the Aulacostephanidae presented here includes the interval of about 5 Ma of the Late Oxfordian and Early Kimmeridgian ranging from the origin of the family to is maximal development. The development and biogeographical distribution of aulacostephanids in Europe were related mostly to sea-level changes and tectonics. The appearance of the ancestor genus Decipia and the following genus Ringsteadia was controlled by marine transgressions during the Late Oxfordian which stimulated also the distribution of these ammonites in Subboreal and Submediterranean Europe. The main faunal turnover at the Oxfordian/Kimmeridgian boundary was related to allopatric speciation correlated to separation of the aulacostephanid assemblages: it resulted in the appearance of the main Ringsteadia-Pictonia-Rasenia lineage in NW Subboreal Europe and the side-lineages Ringsteadia-Vielunia-Eurasenia/Involuticeras and Ringsteadia-Vineta-Balticeras-Rasenioides in NE Subboreal and Central Submediterranean Europe. A strong development of the shallow-water carbonate platforms during the Early Kimmeridgian stimulated the development of still another Pictonia (Pomerania) - Rasenia (Pachypictonia) lineage. The main faunal turnover correlated to a large transgression at the end of the Early Kimmeridgian resulted in the sudden distribution of the new aulacostephanid faunas over large areas of northern and central Europe, and opened a new stage in the evolutionary development of the family.