Angiosperm fossil woods from the Upper Cretaceous (Cardiel Formation) of Argentinean Patagonia

Abstract

We describe nine angiosperm fossil woods from sediments of the Cardiel Formation (Upper Cretaceous) near the Cardiel Lake, Santa Cruz Province, Argentinian Patagonia. On the basis of the characteristics of the anatomy, the specimens were placed in three fossil species: Weinmannioxylon trichospermoides related to the Cunoniaceae, Burseroxylon panzai sp. nov. possibly related to the Anacardiaceae or Burseraceae, and a new taxon with unknown affinity, Tortorellixylon oligoporosum gen. et sp. nov. Angiosperms are 15% of the assemblage and conifers 85%, which is consistent with previous studies of fossil woods from the Late Cretaceous of Patagonia. Most specimens show poorly distinct growth ring boundaries that suggest a weakly marked annual seasonality during the deposition of the Cardiel Formation. In addition, the specimens’ size and the rings’ curvature are consistent with large trees. Decay patterns similar to those produced by modern xylophagous fungi are also recognized in most specimens. The identification of three species in an assemblage of nine fossil woods suggests a significant taxonomic richness of angiosperms, and the taxonomic composition suggests a Late Cretaceous age for the Cardiel Formation (probably Campanian–Maastrichtian). These new records allow a better understanding of the composition of the fossil forests of the Late Cretaceous of Patagonia, in which the tree canopy was apparently dominated by conifers.