A NOVEL ASSEMBLAGE OF DECAPOD CRUSTACEA FROM A TITHONIAN CORAL REEF OLISTOLITH, PURCÃRENI, ROMANIA

A solitary exposure of limestone, in the southwestern section of the Eastern Carpathian Mountains in Romania near Purcãreni, is one of a series of Upper Jurassic limestone blocks contained within Cretaceous-age sediments. These blocks are interpreted to be olistoliths that were emplaced in their present position by gravity movements during the Albian. Movement occurred after underlying Mesozoic units were overthrust upon younger Cretaceous-age flysch deposits. In the area of Purcãreni, the Barremian – Aptian flysch deposits are represented by conglomerates, breccias, sandstones, and marls that make up the “Piscul cu Brazi” Formation. This formation includes several blocks of Tithonian coral reef limestone, the one under consideration having a volume of approximately 320 m3. The blocks are considered to be the result of shallow marine deposition during the retreat of the Tethys Sea. The olistolith at Purcãreni is particularly fossiliferous, and the rich coral reef assemblage yields the decapod crustacean families Prosopidae (Prosopinae, Pithonotinae, two and three species respectively, and Glaessneropsinae), Galatheidae (three species), Dynomenidae (four species), and Axiidae. The limestone blocks from Purcãreni have been studied previously (Murgeanu, Patrulius, and Contescu, 1959; Patrulius, 1959; 1964) however, the authors only mentioned that this location has an abundance of fossils, including decapod crustaceans, and did not provide descriptions or identifications. Distribution of the fossils seems to be haphazard with the exception of one layer approximately one meter thick that yields a higher number of decapod crustaceans in association with a large number of brachiopods. Interestingly, the crabs are represented only by carapaces and disarticulated arms/legs. No articulated crabs were found whereas most associated fauna is articulated.