Calcareous algae from the Lower Oligocene Gornji Grad beds of Northern Slovenia

This paper presents the first systematic account of calcareous algae from t he limestones of the Lower Oligocene Gornji Grad beds of northern Slovenia. These bioclastic limestones are dominated by different coralline algal ass emblages as well as corals, large and small benthic foraminifera as well as bivalves. The taxonomy and growth-forms of eleven species of seven non-gen iculate coralline algal genera are described: Lithoporella, Neogoniolithon, Spongites, Lithothamnion, Mesophyllum, Sporolithon, Subterraniphyllum. Add itionally, the genera Polystrata (Peyssonneliaceae), Halimeda (Halimedaceae ), and Cymopolia (Dasycladaceae) are present. The taxonomic interpretation of fossil coralline material in a manner consi stent with generic and specific concepts currently in use for Recent materi al is, at present, difficult. In the absence of comparative studies on type material, only limited comparisons are possible, and in most cases definit ive taxonomic conclusions cannot be reached. Most of the species designatio ns are thus made following an open nomenclature pending the rigorous taxono mic revision of historically established, fossil coralline algal species. T he present study reveals a considerable variation of growth-form morphologi es at both genus and species levels. This demonstrates the difficulties in using this feature as a diagnostic character in the identification of fossi l coralline red algal taxa.