Late Campanian Rudist Assemblages and Biometrical Analysis of Pseudopolyconites from Bačevica (Eastern Serbia)

Abstract: The lithological and faunal succession cropping out close to the famous palaeontological locality of Bačevica (Eastern Serbia) is described along a very discontinuous and ill-exposed section. Since the section is dominated by clastic sediments, no-vestige of the so-called ‘Vrbovac reef ’ has been observed. Rhythms consisting of a limestone breccia lower unit and a fossil-rich upper part characterize the base of the section while rare silt and sand-rich limestone breccias and prevailing silty/sandy soils are the lithologies observed in the upper part of the same. The faunal succession shows an alternation of monospecific-paucispecific assemblages and much more diverse assemblages of rudists. The stratigraphic distribution of the different examples of rudist bivalves recovered at Bačevica may represent a significant tool for biostratigraphic correlations as far as the late Campanian deposits in the Central Tethys area are concerned. In particular, the Pseudopolyconites-bearing strata seem to be included within a few fossiliferous lithosomes. Therein the Serbian rudistologists instituted twenty species of Pseudopolyconites on the base of the characteristics of their ligamental ridge. Biometrical analyses have been made on the transverse sections of the right valves of the Pseudopolyconites holotypes illustrated in the scientific literature. It is suggested that the wide variability of the ligamental ridge shape alone does not warrant the institution of so many species of the genus in question but the existing ones should probably be re-considered as simple eco-morphotypes