Cupressaceous woods in the Upper Cretaceous Cabullona Group in Fronteras, Sonora, Mexico

Abstract

Recent fossil findings of well-preserved plants in deposits of the Cabullona Group (Campanian-Maastrichtian) indicate that in this region grew an abundant flora. In order to contribute to the knowledge of its paleodiversity, three silicified trunks more than 4 m in length and a stump of 72 cm high discovered close to the town of Fronteras, in sandstones of Campanian age, are described and identified. The fossil wood of these specimens is pycnoxylic and their anatomical characteristics indicate they are typical Cupressinoxylon. Although there is slight anatomical variation among these fossil trunks, they were all included in the same species. The wood anatomy of the fossils does not have a particular affinity to any extant taxa, and among fossil taxa compares closely to Cupressinoxylon, therefore it was assigned to a new species, Cupressinoxylon manuelii Rios-Santos et al. The fluvial and lacustrine deposits suggested by the rocks where the logs were found coincide with the ecological conditions proposed for the growth and reproduction environments these woody plants prefer. To date, another wood pattern has not been found. Although other micro and macro-fossils have been found in nearby locations is probable that this cupressaceous species represent a dominant element in the canopy of the vegetation, which needs more studies in order to propose a full reconstruction.