Latest Albian (Vraconian) brachiopod fauna from North Dobrogea (Romania): taxonomy, palaeoecology and palaeobiogeography

Abstract

The latest Albian (Vraconian) brachiopod fauna from Enisala, in North Dobrogea, includes representatives of rhynchonellids and terebratulids. The rhynchonellids are scarce, representing two families, Cyclothyrididae and Tetrarhynchiidae. The Cyclothyrididae with the subfamily Cyclothyridinae, and the Tetrarhynchiidae with the subfamily Cretirhynchiinae, are represented by rare specimens of ? Cyclothyris sp. and Burrirhynchia cf. sigma SCHWENBACH, 1867), respectively. The terebratulids are very abundant and include representatives of several famili es, as follows: Sellithyrididae, Capillithyrididae, Cancellothyrididae and Terebrataliidae. The Sellithyrididae, which make up the bulk of the assemblage , are represented by two subfamilies: Sellithyridinae with Sellithyris upwarnesis (WALKER, 1870), Boubeithyris boubei (O'ARCHIAC, 1847) and Ovatathyris cf pottemensis OWEN, 1988, and Nerthebrochinae with Harmatosia crassa (O'ARCHlAC, 1847). The Capillithyrididaeare represented by the subfamily Capillithyridinae with Caplllithyris capillata (O'ARCHlAC, 1847). The Cancellothyrididae are represented by the subfamily Cancellothyridinae with numerous specimens of Terebratulinaprotostriatula OWEN, 1988. The Terebrataliidae are represented by the subfamily Gemmarculinae with scarce specimens of Gemmarcula canaliculata (ROEMER, 1840) and Gemmarcula sp. 

The abundance and diversity of the terebratulids in the brachiopod assemblage from Enisala was related to favourable environmental conditions connected with the onset of the marine transgression on North Dobrogea during the latest Albian.

There is a marked stratigraphic lag with some species which in North Dobrogea occur in the latest Albian appearing in the Early Cenomanian in Central and Western Europe . This suggests that North Dobrogea was located on the main route of the westward migration of the mid-Cretaceous brachiopod faunas.