UPPER CRETACEOUS (MAASTRICHTIAN) LANDVERTEBRATE DIVERSITY IN ALBA DISTRICT (ROMANIA)

In Romania, Maastrichtian (Late Cretaceous) dwarf dinosaur remains were first reported from the Haţeg basin by the Baron Franz Nopcsa, at the end of 19th century. Later, the same expanded his research to others areas of Transylvania, adding new localities with comparable Maastrichtian vertebrate assemblages in Alba and Sălaj Counties. Following Nopcsa, both these regions and topics have not been studied for a long time. In the last decade, new field works succeeded in finding rich and diverse Maastrichtian terrestrial vertebrate fauna in Alba County restricted to a distinct Late Cretaceous sedimentary area (Metaliferi). For these studies, the Şard Formation is of main interest. In this formation, the Maastrichtian is developed in fluvial system environments which are documented by flood plain overbank and channel fill deposits. Besides fishes, amphibians, birds and mammals, the fossils embrace mainly various dinosaurs such as sauropods, hadrosaurs, ornithopods, ankylosaurs, various small-sized theropods, as well as other reptiles as turtles and crocodilians. Often, the remains are fragmentary and dislocated. Besides the Haţeg basin, the Metaliferi area is the second important region documenting the Maastrichtian terrestrial biota in Romania.

On some local restricted Maastrichtian environments of the "Hațeg Island" (Transylvania, Romania)

The continental Maastrichtian formations from Transylvania are notorious mainlyfor bearing peculiar fossils related to an island realm known as the "Hațeg Island". The thick piles of sedimentary rocks accumulated in fluvial environments. The "red beds" are in dominance. However, local peculiar environments are of interest for specific types of fossilization (plants, invertebrates or vertebrates), i.e. ox-bow lakes or fluvial temporary abandoned channels. In such deposits the fossil record can be different compared to the red beds, especially when the oxygen content was low. Case studies as the ones from Pui (Hațeg Basin) or Oarda de Jos (SW Transylvanian Basin) are exposed. The relationships of fossil taxa and these restricted environments are discussed.