Fossil filamentous microorganisms associated with plants in early terrestrial environments

Microorganisms are ubiquitous in modern environments, where they have a variety of essential functions but little is known about their diversity and roles in early terrestrial environments. The earliest direct evidence of filamentous microorganisms associated with plants occurs around 407 million years ago in landscapes dominated by an herbaceous flora. 100 million years later, forests were well established and associations had increased in diversity. After more than a century since the first descriptions, the need for better understood fossils has renewed interest in their study. New discoveries and advances in imaging methods are beginning to reveal the importance of Cyanobacteria, Fungi and Oomycota and their interactions with plants in early floras.