Eight biohorizons, four of which were previously distinguished in Central Poland and four new ones have been identified as — contradictionis, pommerania, kuteki, and pilicensis, — were identified in the Dorsoplanites panderi zone of the Upper Jurassic Middle Volgian Substage of the European part of Russia on the basis of the succession of ammonites of the Zaraiskites genus. If that sounds like Greek to you, no worries. Just know that they are actively being studied and those geeking out on the finds are happy as clams.
The peculiarities of variations of the ammonite complexes in space and time testify to the stepwise warming during the Panderi Chron and the occurrence of the significant latitudinal temperature gradient in the Middle Russian Sea. Collection & photo of the awesome Emil Black.