Heinrichsiella Patagonica Gen. Et Sp. Nov.: A Permineralized Acrocarpous Moss From The Jurassic Of Patagonia

Premise of research. Today, mosses are the second most speciose lineage of land plants and are important components of many ecosystems. However, in spite of their diversity and ecological importance in the modern biota, mosses are rare in the fossil record, especially prior to the Cenozoic. Therefore, every new report of a pre-Cenozoic moss deeply enriches our understanding of their evolution. Pre-Cenozoic permineralized mosses represent particularly exciting discoveries because a thorough understanding of the organism is possible. Here, we present the first permineralized Jurassic moss. Methodology. A single chert block from the Canadon Nahuel locality of the Jurassic (178-151 Ma) Deseado Massif in Santa Cruz Province, Patagonia, was polished, and the plants within were examined, revealing a moss gametophyte shoot. A thin section of this chert block was cut and subsequently examined using light microscopy. Pivotal results. We describe Heinrichsiella patagonica gen. et sp. nov., an acrocarpous moss with a novel combination of gametophyte features that suggests basal affinities within either the family Polytrichaceae or the family Timmiellaceae. Both of these families are members of a grade within subphylum Bryophytina basal to subclass Bryidae. Heinrichsiella is the oldest member of this grade by at least 15 million years. Conclusions. Heinrichsiella patagonica is the first report of a moss from the Jurassic Deseado Massif hydrothermal cherts of Patagonia. This fossil reveals that stem group members of extant acrocarpous moss families lived during the Jurassic, implicating the Jurassic as a critical time for understanding the evolution of higher-level moss taxa.