Brachyoxylon fossil woods with traumatic resin canals from the Upper Cretaceous Cerro Fortaleza Formation, southern Patagonia (Santa Cruz Province, Argentina)

Abstract

Two silicified fossil woods from outcrops of the Cerro Fortaleza Formation (Campanian, Upper Cretaceous) in Los Hornos Hill, Santa Cruz Province, Argentina are described. Based on their anatomical characteristics, both specimens were assigned to a new species of the fossil genus Brachyoxylon Hollick and Jeffrey, B. patagonicum sp. nov. They are characterized by having distinct growth ring boundaries, absence of axial parenchyma, uniseriate rays, mixed and uniseriate intertracheary radial pitting, and araucarioid cross-fields with 1–8 circular half-bordered pits per cross-field. In turn, one specimen has three rows of axial traumatic resin canals parallel to the growth rings were identified close to the middle of the growth rings or close to the latewood. Approximately 45% of Brachyoxylon species present traumatic resin canals, which suggests that they are a common feature of this fossil genus. Alternatively, the specimen with the canals shows biological remains (hyphae) and wood fungal degradation patterns, which may be thought as some of those of possible organisms contributing to the formation of the resin canals. This record provides fresh evidence attesting to the abundance and widespread distribution of Cheirolepidiaceae in the Cretaceous of Patagonia.