The gymnosperm pollen Shanbeipollenites proxireticulatus Schrank from the Vaca Muerta Formation (Upper Jurassic-Lower Cretaceous), Neuquén Basin, Argentina

This study documents for the first time the occurrence of Shanbeipollenites proxireticulatus Schrank in levels of the Vaca Muerta Formation, Neuquén Basin, Argentina. It represents the first record of this species in high latitudes of the Southern Hemisphere. The Argentinian specimens are associated with useful palynostratigraphical indicators which suggest an early Valanginian age for the palynoflora yielding S. proxireticulatus. Therefore, this finding constitutes the first record from the Cretaceous. This taxon is related to the orders Cycadales/Bennettitales/Ginkgoales. During the Cretaceous in Patagonia cycads and bennettitaleans groups show marked adaptations to warm and strongly seasonal dry climate periodically influenced by volcanic activity. The paleogeographic distribution of the records of S. proxireticulatus, symmetrically located on both sides of the equator, together with its relationship with the climate zones or Biomes, suggest that the parental plants of this pollen grain thrived under warm climate and probably stressed paleoenvironmental conditions. Since the studied sample is located near 1000 m below the Intravalanginian unconformity, and older age (i.e. late Berriasian) cannot be discarded.