Fungi and fungal interactions in the Rhynie chert: a review of the evidence, with the description ofPerexiflasca taylorianagen. et sp. nov.^†

Abstract

The Lower Devonian Rhynie chert is one of the most important rock deposits yielding comprehensive information on early continental plant, animal and microbial life. Fungi are especially abundant among the microbial remains, and include representatives of all major fungal lineages except Basidiomycota. This paper surveys the evidence assembled to date of fungal hyphae, mycelial cords and reproductive units (e.g. spores, sporangia, sporocarps), and presents examples of fungal associations and interactions with land plants, other fungi, algae, cyanobacteria and animals from the Rhynie chert. Moreover, a small, chytrid-like organism that occurs singly, in chain-like, linear arrangements, planar assemblages and three-dimensional aggregates of less than 10 to [Formula: see text] individuals in degrading land plant tissue in the Rhynie chert is formally described, and the name proposed for the organism. probably colonized senescent or atrophied plant parts and participated in the process of biological degradation. The fungal fossils described to date from the Rhynie chert constitute the largest body of structurally preserved evidence of fungi and fungal interactions from any rock deposit, and strongly suggest that fungi played important roles in the functioning of the Early Devonian Rhynie ecosystem.This article is part of a discussion meeting issue 'The Rhynie cherts: our earliest terrestrial ecosystem revisited'.

Palaeontology: The Rhynie Chert Is the Gift that Keeps on Giving

“…Due to the close relatedness of the two species, this presents the opportunity to use modern humans as a natural experimental system to test for the phenotypic effects of Neandertal genetic variants. To date, Neandertal alleles have been mapped to a range of phenotypic traits in living humans, including height, hair texture and even the likelihood of sneezing after eating dark chocolate [6]. Moreover, the gene variants acquired from Neandertals may have benefited modern humans in various ways, for example by improved immunity to pathogens [7].…”

“…However, the Rhynie chert is not only remarkable for preserving the biota in situ [4], it also preserves the organisms with unbelievable fidelity. This includes organisms that are only rarely, if ever, preserved in normal conditions (for example, fungi and nematodes) [5][6][7] and parts of organisms seldom preserved (such as the enclosing callose wall of developing spores) [8].…”

“…In recent years attention has been drawn to this often-neglected aspect of terrestrial ecosystems -the microbial realm. There has been a continuous stream of new discoveries of bacteria (including cyanobacteria) [17], fungi [5,6], algae [18] and even peronosporomycetes (oomycetes, or water molds) [19].…”

Further evidence for fungivory in the Lower Devonian (Lochkovian) of the Welsh Borderland, UK

“…The chert contains plants growing in situ, terrestrial animals such as arachnids, springtails, myriapods and nematodes, pools containing crustaceans and abundant fungi, both aquatic and those colonising both dead and living plants (Edwards et al 2017 and papers therein). Such fungi have transformed our understanding of their early diversity and ecological roles (Taylor et al 2015;Krings et al 2017). Perhaps, the most surprising recent discovery is the identification of Prototaxites, an organism composed of diverse branching tubes in axes ranging from a few millimetres to 8 m in length and 1 m in diameter, as a basal ascomycete based on inoperculate, polysporous asci lacking croziers (Honegger et al 2017).…”

Filamentous green algae from the Early Devonian Rhynie chert

“…Preservation is exceptional in that: (i) the ecosystems are preserved intact and in their entirety, including components that are not normally preserved such as fungi (e.g. Krings et al 2017a) and algae (e.g. Edwards and Lyon 1983); (ii) much of the biota was exceptionally preserved by the silicification process.…”