The Platysphinctes immigration event in the Middle Oxfordian of the Polish Jura Chain (Central Poland)

Ammonites of the subgenus Platysphinctes, represented by the species Perisphinctes (Platysphinctes) perplanatus (TINTANT, 1961), both microconchs, were recently found in the Middle Oxfordian of the Częstochowa Upland (Polish Jura Chain, Central Poland). Their appearance marks an invasion of ammonites of Mediterranean affinities into the Submediterranean Province. This episode is represented in the studied succession by a distinct horizon, named herein the Platysphinctes event - horizon, that is located in the upper part of the newly erected Arkelli Subzone of the Plicatilis Zone. An emended description of Perisphinctes (Platysphinctes) perplanatus and a description of a new species, Perisphinctes (Otosphinctes) arkelli sp. nov. are provided