Age: early Devonian
The Rhynie Chert contains exceptional plant and animal fossils, many preserved at cellular level. These fossils show the most diverse Early Devonian terrestrial and freshwater community in the world, and they shed light on the colonisation of the land by the earliest land plants.
Various floral remains have been found in the Rhynie Chert, including higher (vascular) land plants, lower (non-vascular) land plants, and even rooting systems. The higher land plant remains have been identified by the presence of diagnostic features, such as cuticle (a waxy covering which protects the delicate parts of the plants to retain moisture), stomata (pores which allow the plant to absorb/remove gas and moisture), vascular tissue (to conduct water through the plant), and spores. Seven higher land plants have been identified so far, including Rhynia, Horneophton, and Aglaophyton. The non-vascular land plants include algae, fungi, and lichens.
|Diagrammatic reconstruction of Rhynia (after Edwards, 1980)||Diagrammatic reconstruction of Aglaophyton (after Edwards, 1986)||Diagrammatic reconstruction of Horneophyton (after Eggert, 1974)|
The Rhynie Chert fauna includes animals which lived in both terrestrial and freshwater environments. The fauna is much less abundant than the flora, because only the animals that were caught by the hot spring waters were preserved. Arthropods (a group of invertebrates that includes arachnids and insects) dominate. Six major groups of arthropods have been identified (although there may be more), including trigonotarbid arachnids (a primitive type of spider that does not spin a web), millipedes, mites and crustaceans.
The level of in-situ preservation in the Rhynie Chert is so good that information can be gathered about the interactions between the plants and animals. Several plants seem to have had defensive mechanisms: Sawdonia is covered with spines, which have dark tips. In modern plants, dark tips are used to secrete a noxious material, as a form of chemical defence. Even some sporangia from the Rhynie plants have spines. It therefore seems likely that the plants developed these defences in response to being attacked. There is also evidence of wounding on some plants, perhaps from attack by mites, or other sap-suckers.