The southwesternmost record of late Silurian (Pridolian) early land plants of Gondwana.

Abstract

The Silurian constitutes a key period in the evolutionary history of land plants. However, records of Pridolian plants in western Gondwana are scarce, limited to outcrops located in southern Bolivia. In this contribution, an association of fossil plants housed in the Rinconada Formation, San Juan Province,Argentina, is presented. This association corresponds to fossil remains of primitive flora with reproductive structures and sterile axes linked to basal tracheophytes. The fossil assemblage is composed of Salopella marcensis, Hostinella sp, Aberlemnia caledonica, Cooksonia paranensis, C. pertoni, C. cambrensis, Steganoteca striata, Isidrophyton sp, Caia langii, two morphotypes of doubtful taxonomy, and graptolites colonies. The association between flora remains and graptolites, represents a parautochthonous fossil assemblage in an inner marine platform, dominated by gravity flows. This fossil record has paleophytogeographic importance since it allows extending the northwest Gondwana-southern Laurrusia unit to more southern areas of Gondwana. This expansion would have been favoured by the post-glacial climatic improvement of the late Silurian, together with a great radiation capacity and environmental flexibility of the flora. Furthermore, this contribution extends the biocron of three South American taxa (A. caledonica, C. paranensis and Isidrophyton sp) first known from the Lochkovian, to the Pridoli. Keywords: Early land plants, Pridoli, Gondwana, Paleophytogeography, Rinconada Formation.