Pragian Epoch
Age of the Rhynie Chert
Pragian is the second stage of the Early Devonian that occurs after the Lochkovian, and before the Emsian. It is also known as the Siegenian in North America
Geologic age
410.8±2.8 - 407.6±2.8 Ma
Eon / Era/ Period / Epoch
Additional Resources
History and contemporary significance of the Rhynie cherts (Edwards et al. 2017)
Ancient bacteria species colonizing land with early land plants (Phys.org 11Sep2023)
Strullu-Derrien et al. (2023) Hapalosiphonacean cyanobacteria (Nostocales) thrived amid emerging embryophytes in an early Devonian (407-million-year-old) landscape
What happened during this time?
Rhynie Chert
The exquisitely preserved Rhynie Chert (410 Ma)
Environment preserved amazing details from Early Devonian
The chert was formed when silica-rich water from volcanic springs rose rapidly and petrified the early terrestrial ecosystem, in situ and almost instantaneously
Plants
Sporophytes of horneophytes, aglaophytes, rhyniophytes, zosterophylls, Asteroxylon
Gametophytes of horneophytes, aglaophytes, rhyniophytes, zosterophylls
Cyanobacteria & Green algae
Lichens
Winfrenatia is the oldest known terrestrial lichen
It comprises a thallus, made of layered, aseptate hyphae, with a number of depressions 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 photosynthetic partner of photobiont resembles the coccoid cyanobacteria Gloeocapsa and Chroococcidiopsis.
There may be two separate algae, making the lichen a symbiosis of three organisms.
Fungi: some of the earliest evidence of mycorrhizae fungi in Earth's history.
Vescicular Arbuscular Mycorrhizae (VAM) found in the rhizome of Aglaophyton major
Glomerocyetes and possible ascomycetes found at locality
Rhizophydites matryoshkae, a chytrid, was found on the in situ spores on Horneophyton lignieri (Krings et al 2021)
Potteromyces asteroxylicola appears to be an Ascomycete that colonized the aerial axes and leaf-like appendages of Asteroxylon mackiei
The fungus is represented by a stroma-like structure and by conidiophores originating in tufts from beneath the cuticle, which caused a reaction in the plant that gave rise to dome-shaped surface projections
This suite of features in the fungus together with the plant reaction tissues provides the earliest unequivocal fossil evidence of a plant pathogenic fungus
Nematophytes: organisms of unknown plant or fungal origin
Invertebrates
Tydeid mites, trigonotarbid "spiders", harvestmen, myriapods, springtails, water fleas, fairy shrimp
Coprolites indicate that invertebrates were feeding on spores
Non-Rhynie Localities
Bryophyta: Sporogonites
Others: Amplectosporangium, Catenalis, Chakassiophyton, Changwuia, Dawsonites, , Hostinella, Margophyton, Minusia, Psilophytites, Sciadocillus, Stachyophyton, Wahnbachella,
Rhyniophytes and Cooksonioids such as Celatheca,Cooksonia, Eogaspesia, Hedeia, Hsüa, Huia, Rhynia, Salopella, Sartilmania, Sciadophyton, Sennicaulis, Stockmansella, Uskiella, Yarravia
Zosterophylls such as Adoketophyton Bathurstia, Deheubarthia, Demersatheca, Discalis, Distichophytum, Gosslingia, Guangnania, Gumuia, Hicklingia, Nothia, Oricilla, Ramoferis, Sawdonia, Taeniocrada,Tarella, Trichopherophyton, Thrinkophyton, Ventarura, Wenshania, Yunia, Zosterophyllum
Lycopods such as Asteroxylon, Baragwanathia, Cervicornus, Drepanophycus, Estinnophyton, Halleophyton, Hueberia, and Zhenglia
Barinophytes including Bracteophyton, Dibracophyton, Krithodeophyton, Pectinophyton, Protobarinophyton
Basal euphyllophytes are also found in other (non-Rhynie) localities such as Psilophyton and Polythecophyton
Pauthecophyton from Yunnan, China (Xue et al. 2012)
Armoricaphyton from Montjean-sur-Loire, France (Gerrienne and Gensel 2016)
Eophyllophyton, from China, is one of the first euphyllophytes with flattened appendages that appear to be small leaves (Hao 1988, Hao and Beck 1993)
This is a possible early progymnosperm, although this taxonomic placement is disputed.
