New plant fossil records and biostratigraphic analysis from the Uspallata Group (Late Triassic) at Cacheuta Hill, Cuyo Basin, west-central Argentina

Abstract

The Cacheuta Hill (Precordillera, Mendoza province, Argentina) is a classic locality of the Gondwanan Triassic. In this contribution, new fossil plant records in the Uspallata Group are described, the systematic palaeontology of previously described taxa is revised, and a comprehensive analysis of the Triassic palaeoflora from Cacheuta Hill is undertaken. The studied unit was correlated with other Triassic formations of Gondwana. Our revision of the plant-fossil record from the Uspallata Group provides the first record of the genus Androstrobus (Cycadales) and Odyssianthus (Voltziales) in the Argentinean Triassic; the description of Rissikianthus as a new element of the Cacheuta palaeoflora; the transfer of Baiera rollerii to Rochipteris rollerii; and the presence of Hamshawvia and Stachyopitys in the Argentinean Triassic, confirming the record of these reproductive structures as related to the ginkgoalean lineage. The Potrerillos Formation shows greater similarities with the Carrizal Formation (Argentina) and the Molteno Formation (South Africa). The palaeoflora of the Cacheuta Formation is correlated with that of the Ischigualasto Formation (Argentina) and the Molteno Formation (South Africa). The plant fossil assemblages present in the Uspallata Group at Cacheuta Hill indicate a Late Triassic (Carnian–Norian) age for the unit.