Ediacara biota
A diorama depicting an out-of-date interpretation of
Ediacaran life-forms.
The Ediacara (IPA: /ˌiːdiˈækərə/, formerly Vendian) biota
are ancient life-forms of the Ediacaran Period, which
represent the earliest known complex multicellular or-
ganisms.[note 1] They appeared soon after the Earth
thawed from the Cryogenian period’s extensive glaciers,
and largely disappeared soon before the rapid appear-
ance of biodiversity known as the Cambrian explosion,
which saw the first appearance in the fossil record of the
basic patterns and body-plans that would go on to form
the basis of modern animals. Little of the diversity of the
Ediacara biota would be incorporated in this new
scheme, with a distinct Cambrian biota arising and
usurping the organisms that dominated the Ediacaran
fossil record.
The organisms of the Ediacaran Period first appeared
around 580 million years ago and flourished until the
cusp of the Cambrian 542 million years ago, when the
characteristic communities of fossils vanished. While
rare fossils that may represent survivors have been
found as late as the Middle Cambrian (510 to 500 million
years ago), the earlier fossil communities disappear from
the record at the end of the Ediacaran, leaving only con-
troversial fragments of once-thriving ecosystems, if any-
thing.[1] Multiple hypotheses exist to explain this disap-
pearance, including preservation bias, a changing envir-
onment, the advent of predators, and competition from
other life-forms.
Some Ediacaran organisms might have been closely
related to groups that would rise to prominence later;
for instance, Kimberella shows some similarity to mol-
luscs, and other organisms have been thought to show
bilateral symmetry, though this is controversial. Most
microscopic fossils are morphologically distinct from
later life-forms: they resemble discs, mud-filled bags, or
quilted mattresses. Classification is difficult, and the as-
signment of some species even at the level of kingdom —
animal, fungus, protist or something else — is uncer