The Rhynie Chert preserves one of the oldest terrestrial ecosystems, which is a hot spring environment. It's Lower Devonian, and the oldest know harvestman was also found there. These are some photographs of my thin sections from this environment.
This first thin section is one of my favourites, it has several Aglaophyton major plants that contain fungal cysts of Palaeomyces gordoni, containing spores.
These are more Aglaophyton major cross sections. In this and the one above, there are a few vascular bundles, these consist of thin-walled protoxylem cells