Lower Ordovician cystoids (Rhombifera, Diploporita) from the Praque Basin (Czech Republic)

Abstract

Seven cystoid taxa, including one new species, are described or re-described from the Třenice and Mílina formations (Lower Ordovician, upper Tremadocian) of the Prague Basin: Macrocystella cf. greylingi, Echinosphaerites concomitans, E. sp., Glyptosphaerites ferrigena, Paleosphaeronites crateriformis, P. grossularia and Pyrocystites sp. New data on the morphology of Paleosphaeronites, i.e., gonoduct canal and palatal plates in peristome, are presented. A fixo-sessile mode of life of Paleosphaeronites is documented by the specimens attached to trilobite exoskeletons. The described cystoid fauna is one of the earliest yet known, and indicates remarkable echinoderm diversity and favourable marine environment in the late Tremadocian in the European part of peri-Gondwana region.