Middle Triassic gastropods from the Besano Formation of Monte San Giorgio, Switzerland

A rare discovery of Middle Triassic gastropods from the Besano Formation at Monte San Giorgio, Switzerland, sheds light on the biodiversity and paleoecology of the Anisian/Ladinian boundary. The study documents five taxa—Worthenia (Humiliworthenia)? aff. microstriata, Frederikella cf. cancellata, ? Trachynerita sp., and two ? Omphaloptycha species—representing the clades Vetigastropoda, Neritimorpha, and Caenogastropoda. These specimens, among the best preserved in the formation, suggest that small gastropods may have thrived as pseudoplankton or free-swimming larvae under anoxic conditions, while larger forms were likely transported by sediment disturbances. The findings challenge previous interpretations of the Besano Formation's depositional environment and highlight its significance for understanding Triassic carbonate platform ecosystems.

Pieroni, V., & Furrer, H. (2020). Middle Triassic gastropods from the Besano Formation of Monte San Giorgio, Switzerland. Swiss Journal of Palaeontology, 139(1). https://doi.org/10.1186/s13358-019-00201-8