First freshwater medusoids in the Permian from Africa: Implications for the palaeoenvironmental, palaeogeographic and stratigraphic distribution of Medusina atava

Abstract

A recent palaeontological and sedimentological prospecting conducted in the Marrakech High Atlas (Morocco) yielded fossils of Permian medusoids at Taddart (lower part of the Cham-el-Houa Siltstone Formation, Tissiyyi Basin). Some specimens show details of the radial canals and the manubrium. Based on comparisons with the European record, the specimens can be safely ascribed to Medusina atava. They correspond to the first Permian freshwater medusoids from Gondwana and provide crucial information for the reconstruction of equatorial ecosystems during the Permian. The specimens were fossilized in open lacustrine deposits, more specifically in high-density turbidite facies. This discovery (1) contrasts markedly with most European palaeontological sites yielding M. atava, where specimens are preserved in proximal lacustrine deposits formed in shallow-water, periodically emerged environments, (2) expands the palaeogeographic distribution of Permian freshwater medusoids beyond the northern hemisphere, into the equatorial zone, and (3) extends the stratigraphic range of the species M. atava from the early to the middle/late Permian.