Rhynie chert, an early land ecosystem

The Rhynie chert is a layered rock near the village of Rhynie in Aberdeenshire, Scotland, formed about 407 million years ago in the Early Devonian. William Mackie, a local doctor and geologist, noticed it in 1912, and Robert Kidston and William Lang described its fossils in a series of papers from 1917 to 1921. Hot springs fed by volcanic activity repeatedly flooded a marshy plain with silica-rich water, which hardened into chert and trapped whole plants and animals in place.¹²

Slices of the chert show tiny plants such as Rhynia, Aglaophyton and Asteroxylon standing a few tens of centimetres high, with simple stems and no leaves, and cells that can be counted under a microscope. Roots hosted fungi that formed a partnership with the plants, an early form of the mycorrhizal links most plants still use. Other fossils include nematode worms, mites, a springtail named Rhyniella and Rhyniognatha, a mandible some think came from an early winged insect. A lichen-like partnership, Winfrenatia, is also known.¹²

The site is the best view of how life colonised the land. It shows a complete early ecosystem, from algae and fungi through plants to herbivores and predators, rather than isolated fossils, and its detail helps date the origins of roots, spores and soil animals. Several features of today's land life, including soils, mycorrhizas and food webs of small arthropods, are already visible.¹