PARASCOLYMIA (SCLERACTINIA: LOBOPHYLLIIDAE) IN THE CENTRAL PARATETHYS SEA (AUSTRIA) AND ITS BIOGEOGRAPHIC IMPLICATIONS

Palaeobiogeographical and palaeodiversity patterns of scleractinian reef corals are generally biased due to uncertain taxonomy and a loss of taxonomic characters through dissolution and recrystallization of the skeletal aragonite in shallow marine limestones. A fossil lobophylliid coral in mouldic preservation was discovered in the early middle Miocene Leitha Limestone of the Central Paratethys Sea (Vienna Basin, Austria). By using grey-scale image inversion and silicone rubber casts for the visualization of the original skeletal anatomy and the detection of distinct micromorphological characters (i.e. shape of septal teeth, granulation of septocostae) Parascolymia bracherti has been identified as a new species in spite of the dissolved skeleton. The current distribution of Parascolymia is, like all representatives of the Lobophylliidae, restricted to the Indo-Pacific region, where it is represented by a single species only. Parascolymia bracherti proves the genus also in the Miocene Mediterranean reef coral province. Reviewing the spatio-temporal relationships of fossil corals related to Parascolymia indicates that the genus was probably rooted in the Eastern Atlantic‒Western Tethys region during the Paleocene to Eocene. This occurrence corresponds to the former center of marine biodiversity. It also reveals an obvious temporal and spatial coincidence between the dispersal of Parascolymia and the displacement of the marine biodiversity hotspot into the present Indo-West Pacific region. Parascolymia is thus an example of a successful transformation of an originally Tethyan element contributing to the present biodiversity in the Indo-West Pacific. The revealed palaeobiogeographical pattern shows an obvious congruence with that of the coral Acropora and tridacnine bivalves reflecting a gradual equatorwards retreat of the marine biodiversity center parallel to the Cenozoic climate deterioration. The gradual nature of this palaeobiogeographic change implies an important climatic control contrasting the hypothesis of a primarily tectonically driven hopping of geographically distinct biodiversity hotspots in the Cenozoic.