Coniferous woods from the Albian (Piedra Clavada Formation) of Argentine Patagonia

Abstract

Five samples of silicified fossil woods were collected from the Lower Cretaceous Piedra Clavada Formation, Santa Cruz Province, Argentina. The preservation of the fossil woods varies. Two very poorly preserved specimens are classified as ‘‘indeterminate conifers”. Based on the wood anatomy of the remaining specimens, we identified two taxa: Brachyoxylon patagonicum (one specimen), possibly related to the extinct conifer family Hirmeriellaceae, and cf. Brachyoxylon/Agathoxylon (two specimens), possibly related to the Hirmeriellaceae or the Araucariaceae. All samples have distinct growth ring boundaries, indicating annual seasonality. Furthermore, the curvature of the rings and the minimum estimated diameter suggest that the woods came from mature trees. Decay patterns resembling those induced by contemporary xylophagous fungi were identified in one specimen. The presence of fossil woods possibly related to the Hirmeriellaceae and Araucariaceae in the Piedra Clavada Formation is consistent with previous palynological studies of this stratigraphic unit. These records support the dominance of conifers in the Early Cretaceous forests of Argentine Patagonia.