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Ediacaran biota: the first large animals
c. 575–539 million years ago· Event· Life & early humans
Well documentedSolid records, physical evidence or scientific consensus.
Earth's first large, complex organisms, soft-bodied creatures shaped like fronds, discs and quilts, lived on the seafloor.
See it on the History map →What happened
Named after the Ediacara Hills of South Australia, these organisms appear about 575 million years ago. Most had no mouths, shells or legs; many probably absorbed food from seawater. Some, like the oval Dickinsonia, are now accepted as early animals; others may be extinct experiments with no living relatives. Most vanished by about 539 million years ago.
Why it matters
They show that large life existed before the Cambrian explosion, and they record the first steps toward animal bodies.
How we know
Fossil imprints in sandstone in Australia, Newfoundland, Namibia and Russia. A 2018 study found cholesterol-type molecules in Dickinsonia fossils, marking it as an animal.
Still debated
What many of these creatures were, and why most disappeared (new predators or changing seas), is still debated.
Connections (3)
▸Multicellular life led to Ediacaran biota: the first large animalsWell documented
The connection
After about a billion years of mostly small, simple multicellular forms, larger and more complex organisms appeared. The Ediacaran creatures were among the first big enough to see without a microscope, some over a meter long, showing how far multicellular life had come.
When and how
On shallow and deep seafloors from about 575 million years ago; named for the Ediacara Hills, South Australia, where geologist Reginald Sprigg found them in 1946.
How we know
Fossils show a clear sequence: microscopic and small multicellular forms come first, then the large Ediacaran organisms.
Debates and open questions
How Ediacaran organisms relate to earlier forms and to modern animals is still unclear.
▸Snowball Earth may have spurred Ediacaran biota: the first large animalsDebated
The connection
As the last great freeze ended about 635 million years ago, melting glaciers washed nutrients into the oceans, and oxygen levels may have risen. Some scientists argue these changes let larger, oxygen-hungry organisms appear soon after, in the Ediacaran Period.
When and how
In the oceans after the Marinoan glaciation ended, about 635–575 million years ago.
How sure are we?
The sequence fits: big Ediacaran fossils follow the thaw. Chemical evidence for an oxygen rise exists but is disputed, so the link is unproven.
Debates and open questions
Whether the freeze-thaw cycles caused, helped, or merely came before the rise of large life is debated.
▸Ediacaran biota: the first large animals gave way to Cambrian explosionWell documented
The connection
Most Ediacaran organisms disappeared around 539 million years ago, possibly pushed out by new burrowing and predatory animals. Their decline opened space for the far more varied Cambrian animals, with shells, eyes and legs, that rapidly took over the seas.
When and how
On seafloors worldwide, at the start of the Cambrian Period, about 539 million years ago.
How we know
Fossils show Ediacaran forms vanishing as Cambrian animals and their burrows increase; the transition is well recorded in rock layers.
Debates and open questions
Whether the Ediacarans were outcompeted, eaten, or wiped out by environmental change is debated.