LAUSR

Abstract New fossil plants are described from the Ischichuca Formation (Middle?–Late Triassic), La Rioja province, northwestern Argentina. A systematic description of Heidiphyllum leaves, ovulate structures of Dordrechtites and undetermined conifer wood is provided. This is the first description of these elements for the Ischichuca Formation, and the first illustration of Dordrechtites from South America, thus extending the Gondwana distribution. Two species of Heidiphyllum are described: H. elongatum and H. minutifolium. Special interest is paid to the taxonomic assignment of Dordrechtites, which has been interpreted by several authors, based on morpho-anatomic features, as a member of different groups (i.e. Voltziales, Coniferales (=Pinales), Dordrechtitales, Corystospermales (=Umkomasiales) and other seed ferns. Herein Dordrechtites is interpreted as a gymnosperm ovule-bearing organ with foliar cupules, related to seed ferns.