Life › Complex cells & first multicellular life › Ediacaran biota
Dickinsonia
c. 558 million years ago; animal status backed by 2018 biomarkers· Fossil or site· Animals
Strong evidenceGood evidence; dates or details still being refined.
A flat, oval, ribbed Ediacaran organism, up to about 1.4 meters long, now widely accepted as one of the earliest animals.
See it on the Life map →What happened
Named in 1947 by Reg Sprigg after Ben Dickinson, a South Australian mines official, Dickinsonia was variously called a jellyfish, worm, lichen, fungus or giant single cell. It had no mouth or gut; it apparently lay on microbial mats, absorbed food through its underside, and moved, leaving faint feeding traces. In 2018 researchers found cholesterol-type molecules in its preserved organic film from Russia's White Sea cliffs, a chemical hallmark of animals.
Why it matters
For most researchers it settled a 70-year argument and showed that large animals lived about 558 million years ago, roughly 20 million years before the Cambrian explosion.
The evidence (fossils, genes, rocks)
Thousands of fossils from Australia and Russia; steroid biomarkers extracted by Ilya Bobrovskiy, Jochen Brocks and colleagues (Science, 2018); growth patterns and trace fossils.
Still debated
Where it fits on the animal family tree is unclear, and a few researchers question whether the biomarkers really came from Dickinsonia itself.
Connections (2)
▸Dickinsonia is early chemical evidence of First animalsStrong evidence
The connection
Dickinsonia was not the first animal, but it is among the earliest whose animal identity is backed by chemical evidence. Its fossils preserve cholesterol-type steroids that animals make, showing that large animals existed by about 558 million years ago, after decades of doubt.
When and how
White Sea coast of northwestern Russia, about 558 million years ago; Ilya Bobrovskiy and colleagues published the result in Science in 2018.
How sure are we?
The organic film was dominated by cholesteroids, unlike the algal and microbial sterols in surrounding mat material.
Debates and open questions
A minority argues the steroids could come from decaying mats or other sources; where Dickinsonia branches among animals is unresolved.
▸Ediacaran biota includes DickinsoniaWell established
The connection
Dickinsonia is one of the best-known members of the Ediacaran biota, with thousands of specimens. Like many of its neighbors it lived on microbial mats and had a quilted, segmented-looking body, which makes it a key test case for what the Ediacaran organisms were.
When and how
Ediacara Hills, South Australia, where Reg Sprigg named it in 1947, and the White Sea coast of Russia, about 560–550 million years ago.
The evidence
It occurs in the same fossil beds as fronds and other Ediacaran forms, preserved in the same way.
Debates and open questions
Whether other quilted Ediacaran forms were also animals; Dickinsonia's result does not settle the identity of fronds such as Charnia.