Rhynie chert

The bed is under at least 1 metre of overburden, in a small field near the village of Rhynie, so is effectively inaccessible to collectors; besides which, the site is a Site of Special Scientific Interest. A second unit, the Windyfield chert, is some 700 m from the Rhynie. The Rhynie chert extends for at least 80 m along strike and 90 m down-dip. ==History of research==

The chert was discovered by William Mackie while mapping the western margin of the Rhynie basin in 1910–1913. Until recently, the Rhynie chert was the only such deposit known from the geological record, although recent work has turned up other localities from different time periods and continents. ==Conditions of formation==

The chert was formed when silica-rich water from volcanic springs rose rapidly and petrified the early terrestrial ecosystem, in situ and almost instantaneously, interbedded with sands, shales and tuffs - which speak of local volcanic activity. Deposition was very rapid. river flowing to the north periodically deposited the sandy layers found in cores when it flooded its banks. Sedimentary textures which appear to have formed in the hydrothermal vents themselves are preserved with a brecciated texture; ==Preservation==

Plants The preservation of plants varies from perfect three-dimensional cellular permineralisation to flattened charcoal films. On occasion, plants may have their vertical axes preserved in growth position, with rhizoids still attached to rhizomes; even the plant litter is preserved. The analysis of rhizomes and rhizoids makes it possible to discern which plants had an active water uptake system (e.g. Horneophyton), and which were likely to have colonised waterlogged surfaces (Asteroxylon). The chert also allows the identification of the gametophyte phases of taxa such as Aglaophyton. Analysis of spores shows that the flora was lacking in some elements common elsewhere at this time, likely due to its setting in a mountainous region, rather than in a lowland flood plain like most other fossil deposits. • Aglaophyton • Asteroxylon • Horneophyton • Nothia • Rhynia • Trichopherophyton • Ventarura Another group, Nematophytes, remains enigmatic, but may represent aquatic land plants. Algae Several putative chlorophytes have been discovered in the Rhynie assemblage (Mackiella and Rhynchertia). A well-preserved charophyte, Palaeonitella, Arthropods As a result of its exquisite preservation, the Rhynie chert boasts the most diverse non-marine fauna of its time, Typical members of the Rhynie chert arthropod fauna include the crustacean Lepidocaris, the euthycarcinoid Heterocrania, the springtail Rhyniella, the possible insect Leverhulmia, the harvestman Eophalangium sheari, The oldest known hexapod (Rhyniella praecursor), which resembles the modern springtails, was found in the Rhynie chert, pushing dates for the origination of hexapods (a group that includes the insects) back to the Silurian period. Fungi Fungi known from the Rhynie chert include the chytridiomycetes, ascomycetes, oomycota (Peronosporomycetes) and glomeromycetes; The fossils are filamentous, around 3 μm in diameter, and grew on plants and the sediment itself. They occasionally form structured colonies which go on to create microbial mats. Lichens A new genus of lichen, Winfrenatia, has been recovered from the Rhynie chert. The lichen comprises a thallus, made of layered, aseptate hyphae; a number of depressions are formed on its top surface. Each depression contains a net of hyphae holding a sheathed cyanobacterium. The fungus appears to be related to the Zygomycetes, and the photobiont resembles the coccoid Gloeocapsa and Chroococcidiopsis. == Paleobiota ==

Animals Plants and Multicellular Algae Fungi Other taxa ==Interactions==

The Rhynie chert, by preserving a snapshot of an ecosystem in situ in high fidelity, gives a unique opportunity to observe interactions between species and kingdoms. wounds in various states of repair, and the mouthparts of arthropods. In addition, a fossil enoplid nematode named Palaeonema parasitised Aglaophyton plants, with eggs, juveniles and adults all recorded from within their stomatal chambers. Coprolites - fossilised droppings - give a useful insight of what animals ate, even if the animals cannot be identified. Coprolites found in the Rhynie chert are typically between 0.5 and 3 mm in size, and contain a variety of contents. Analysis of coprolites allows the identification of different feeding modes, including detritovory and herbivory; some coprolites are so densely packed with spores that it is possible that these made up a substantial proportion of some organisms' diets. it is possible for many of the arthropods to deduce their likely ecological role, however, it is unclear if this community was representative of a typical terrestrial arthropod community of the time, or rather was specific to the stressed Rhynie environment. Plants responded to fungal colonisation in different ways, depending on the fungus. The rhizoids of Nothia displayed three responses to fungal infestation: the hyphae of some (mutualistic) colonists were encased by plant cell walls; other (parasitic) fungi were met with typical host responses of increased rhizome cell size; while yet other fungi solicited an increase in thickness and pigmentation of cell walls. Once inside a plant cell, fungi produced spores, which are found in decaying plant cells; ==See also==