Earliest occurrence of the Hirnantia Fauna in the Prague Basin (Czech Republic)

The Hirnantia Fauna was observed at a new stratigraphic level in the topmost Kraluv Dvur Formation at Praha-Reporyje. Up to now this distinctive late Ordovician fauna has been known only from the summit of the Kosov Formation in the Prague Basin. The newly observed fauna consists of draboviids Hirnantia sagittifera, Kinnella kielanae kielanae, taxonomically poor ostracods, a machaeridian Lepidocoleus, a new undetermined carpoid, and the very rare Mucronaspis. The fauna is much poorer than the fauna of the 'Pernik Bed' below. The presence of the Hirnantia Fauna at this new level indicates a significant cooling and eustatic fall in the sea level resulting in a shallow subtidal environment (BA 3-4) prior to the deposition of glaciomarine diamictites at the base of the Kosov Formation.