Ediacaran Period
An age of diversifying complex life
The Ediacaran is the third and final period of the Neoproterozoic Era, occurring after the Cryogenian, and before the Phanerozoic Eon (Paleozoic).
What happens during this time?
Geological
Around 600 Ma, the supercontinent Pannotia began to form briefly until 540 Ma
Glaciations during the early part of the Ediacaran (Varanger-Marinoan ice ages: 605-585 Ma).
Warm, humid climate during the second part of the Ediacaran (585-542 Ma).
Cooling with glaciation at high latitudes occurred towards the very end of the Ediacaran and the beginning of Cambrian.
Burrowing animals are hypothesized to have stabilized Earth's oxygen levels during Ediacaran - Cambrian transition (Boyle et al. 2014)
The evolution of the first burrowing animals significantly increased the extent to which oxygenated waters came into contact with ocean sediments.
Exposure to oxygenated conditions caused the bacteria that inhabit such sediments to store phosphate in their cells.
This caused an increase in phosphorus burial in sediments that had been mixed up by burrowing animals, which, in turn, triggered decreases in marine phosphate concentrations, productivity, organic carbon burial, and ultimately oxygen.
Because an oxygen decrease was initiated by something requiring oxygen (i.e. the activity burrowing animals), a net negative feedback loop was created
Biological
The Ediacaran is known for the first large scale radiation of multicellular life.
Most Ediacaran biota do not survive into the Cambrian.
Some researchers propose that this is the first mass extinction caused by decreased global oxygen availability (Evans et al. 2022)
"Evolutionary innovation, ecosystem engineering, and biological interactions may have ultimately caused the first mass extinction of complex life" during this time (Darroch et al. 2015)
Prokaryotic
Possible microbial life on land, as early as 580 Ma, although this evidence will need to be corroborated by other researchers (Univ. of Santa Cruz, 2017).
Fungi
Evidence of fungal chytrids
Possible fungal hyphae preserved in silica dolostone of South China (Gan et al. 2021)
This could represent the oldest known terrestrial fungi in the fossil record
Algae
Evidence of multicellular algae, Chinggiskhaania bifurcata (Dornbos et al. 2016)
Protocodium sinense, from China dated to 541 Ma, was an ulvophyte green alga
Like living ulvophytes, Protocodium was siphonous and similar in structure to living Codium
This fossil demonstrates that by the end of the Proterozoic, the green algae had diversified to modern levels
Fauna
The rise of early animals dramatically changed the prehistoric environment, replacing earlier organism of the Precambrian
Early animals formed complex ecological communities; species were becoming more specialized and engaging in more inter-species interactions towards the end of the Ediacaran era (Eden et al. 2022)
This trend, often seen during ecological succession, points to competitive exclusion, rather than mass extinction, as the cause of the diversity drop in the late Ediacaran period
Diversification of metazoans
Trace fossils of some metazoan, Trichophycus pedum
Aspidella (610 Ma)
Simple, disc-like impressions of soft-bodied organisms
Possibly the foot pedals of sessile cnidarian-like organisms
Cell differentiation in Ediacaran animal embryo-like fossils (~600 Ma) - Chen et al. 2014
Eocyathispongia qiania, one of the earliest sponges (~600 Ma) -Yin et al. 2015
Earliest bilaterians found in Uruguay (~585 Ma)
Charnia masoni (575 Ma)
Frond-like marine organism, attached to seafloor, which grew up to 2 meters in length
Kimberella quadrata (555 Ma)
Cubozoan (box jellies)
Parvancorina and Spriggina (550 Ma)
may have been related to arthropods
Parvancorina may represent an ancestor to the trilobites
Cloudinia (548 Ma)
Small, shelly fossil
Evidence of earliest known reef-building (Penny et al. 2014)
Pteridinium (545 Ma)
An erniettomorph with a 3-lobed body
Above: Fungus-like fossils from South China (Gan et al. 2021)
Above: Reconstruction of an Ediacaran marine environment showing sea fans, jelly fish, and early chordate
Above: Reconstruction of the green alga, Protocodium sinense
Right: Scanning electron micrographs of Protocodium showing 3D structure
Additional Resources
Paleontologists find 635 million-year-old land fungus-like fossils (Sci News Jan 2021)