Fossil mosses: What do they tell us about moss evolution?

Abstract

The moss fossil records from the Paleozoic age to the Eocene epoch are reviewed and their putative relationships to extant moss groups discussed. The incomplete preservation and lack of key characters that could define the position of an ancient moss in modern classification remain the problem. Carboniferous records are still impossible to refer to any of the modern moss taxa. Numerous Permian protosphagnalean mosses possess traits that are absent in any extant group and they are therefore treated here as an extinct lineage, whose descendants, if any remain, cannot be recognized among contemporary taxa. Non-protosphagnalean Permian mosses were also fairly diverse, representing morphotypes comparable with Dicranidae and acrocarpous Bryidae, although unequivocal representatives of these subclasses are known only since Cretaceous and Jurassic. Even though Sphagnales is one of two oldest lineages separated from the main trunk of moss phylogenetic tree, it appears in fossil state regularly only since Late Cretaceous, ca. 70 million years ago (Ma), while earlier they were found twice as small leaf fragments from Lower Jurassic (ca. 200 Ma) and Late Ordovician (ca. 455 Ma). Pleurocarpous mosses appear in fossil state near the border between Jurassic and Cretaceous, although most Cretaceous mosses belong to acrocarps. Only in Eocene amber pleurocarps become more numerous than acrocarps. Some Eocene mosses can be assigned to extant families and sometimes genera, although the majority of Eocene pleurocarps are difficult to identify up to the family, as their morphology often allows placement of a particular specimen into several different families.