Bivalves from the tectonic units of eastern Serbia in the context of the Pliensbachian (Early Jurassic) palaeobiogeography of Europe

An increase in interest to the Pliensbachian palaeobiogeography of Europe makes urgent consideration of palaeontological data from the regions not taken into account earlier. The representative bivalve records of eastern Serbia and some other European territories (a total of 88 species belonging to 42 genera) permits quantitative assessment of similarity of the Pliensbachian faunas with the Jaccard Index, the Czekanowski's Quantified Coefficient, and the Gower Index. It is established that the Pliensbachian bivalves of eastern Serbia are most similar to those of Bulgaria and France; the similarity to several other European territories is moderate and surprisingly almost the same. The similarity of the Pliensbachian bivalves between the Danubian and Infra-Getic tectonic units constituting the territory of eastern Serbia is significant. The interpretation of the results of this study in the light of the palaeobiogeographical reconstructions implies that the Northwestern European biochore is heterogeneous because of different similarity of the regions within this unit. The bivalve fauna of Portugal is relatively more distinct from the other territories considered in this study (Germany, England, France, etc.). Eastern Serbia was located at or near the transition between Northwestern European (Boreal) and Mediterranean (Tethyan) biochores, and its bivalve fauna is the most similar to those of Bulgaria and France. The results of the present study also show that ammonites and especially brachiopods are more suitable tools for the Pliensbachian palaeobiogeographical reconstructions than bivalves.