Corsiniopsis kurtzii gen. Et sp. Nov., a new fertile marchantioid fossil from the late triassic of argentina provides evidence of the evolutionary trends of fertile branches in the complex thalloid liverworts.

Abstract

Background and aims: the complex thalloid liverworts (Marchantiales) are an iconic group of bryophytes that have been long speculated to be one of the oldest lineages of land plants. Even though a thorough review of their fossil record has recently enhanced our understanding of their evolutionary history, few fossils have been found to preserve fertile characters. Here, we describe a new fertile marchantioid fossil from the Late Triassic of Argentina and assess its phylogenetic affinities.

Methods: the new fossil was scored into an extensive morphological matrix encompassing both extant and fossil bryophytes. To thoroughly assess the position of the fossil, phylogenetic analyses applied two taxon samplings: a broad sampling of bryophytes and a focal sampling of Marchantiales. Topologies were inferred under equal weighting and extended implied weighting, including character dependencies as step-matrices complexes. The optimal topologies inferred under equal weighting were finally time-calibrated using the First Appearance Data (FAD) for species.

Key results: our analyses indicate a clear affinity of the new fossil with the xerophytic Marchantiales, although its precise placement within the order depends on the analytical approach. Time-calibrating the optimal topologies led to xerophytic lineages diverging in the interval Late Permian-Early Triassic, which is older than previously inferred. The inclusion of the new fertile fossil implies that specialised branches were undergoing reduction already by the Early Mesozoic.

Conclusions: through the description and analyses of a new Early Mesozoic fossil, our study reveals a novel trend in the evolution of specialised fertile branches in Marchantiales. Likewise, according to our time-calibrating, the radiation of xerophytic lineages is inferred older than in previous studies. Our study highlights the importance of discovering new fossils to close the gap in our knowledge of the evolutionary history of the complex thalloid liverworts.