At around 400 million years old, the Rhynie chert contains an assemblage of fossil plants preserved in sufficient detail that mycorrhizas have been observed in the stems of Aglaophyton major [REF].
Mycorrhizas are present in 92% of plant families studied (80% of species),[REF] with arbuscular mycorrhizas being the ancestral and predominant form,[REF] and the most prevalent symbiotic association found in the plant kingdom [REF].