Revision of "Fitzroya" tertiaria berry based on holotype cuticle and new material with attached female cones, Cretaceous (Cenomanian), Austral Basin, Argentina

Abstract

“Fitzroya” tertiaria Berry is the only South American fossil species still referred to the modern genus Fitzroya (alerce, Cupressaceae). In various publications, the species has also been referred to Dacrycarpus (Podocarpaceae), but without detailed review of the type specimen. We revise the holotype, along with new material from the type locality (Chalia River-Mata Amarilla Formation) and other Cretaceous lo-calities in Santa Cruz (Piedra Clavada Formation). The holotype (USNM-37859) includes twigs with imbricate leaves and cuticle, which we studied nondestructively using fluorescence microscopy and SEM. Our studies rule out the assignment to Fitzroya due to the absence of typical cuticular characters such as stomata in bands and Florin rings, and to all other genera in Cupressaceae ss. due to the lack of whorled phyllotaxis. Affinity to Podocarpaceae is rejected because the holotype has no typical podocarpaceous stomata (paratetracytic), including Dacrycarpus due to the lack of acicular leaves and foliar dimorphism. Our revision places the holotype among the taxodioid Cupressaceae based on the presence of spirally arranged adpressed scaly leaves, cycloctic stomatal apparatus, and Athrotaxis type stomata. Furthermore, the assignement is confirmed with new material in organic connection to a female cone. The presence of raised guard cells, straight subsidiary cell walls, and quadrangular epidermal cells becoming elongated to the leaf margins are shared with Athrotaxis. Thus, the only fossil record of Fitzroya in South America should be rejected in favor of a closer relation with a genus that today lives in Tasmania and has Cretaceous records in southern Patagonia.