Ediacaran Fossils:
Metazoan Origins in the
Proterozoic
Geology 331, Paleontology
The Doushantuo microfossils from
China, 600 Ma
Diploblastic Animals:
Two Tissue Layers
Triploblastic Animals:
Three Tissue Layers
Mesoderm in blue
(jelly)
Life of the Ediacaran, 543-600 Ma
The White Sea assemblage, 560-550 Ma
Ediacara Hills of Australia
Ediacaran
fossils exposed
in sandstone.
How were they
preserved?
A fossil sea pen from
the Ediacaran of
Australia.
Ediacaran fossils
were preserved as
impressions in
gelatinous microbial
mats on the sea
floor.
Modern sea
pens, relatives of
corals
Mawsonites,
a fossil
jellyfish?
A variety of Ediacaran fossils
Dickinsonia – a segmented worm
Kimberella – a probable mollusc
Spriggina –
an arthropod?
Tribrachidium –
what is it?
Arkarua – oldest
echinoderm?
Rangeomorphs
from
Newfoundland
Aspidella from
Newfoundland
Charnia
Charniodiscus
Cloudina
Namacalathus
reconstructed
Calcified organisms
at the end of the
Ediacaran
3D Trace fossils at the Ediacaran-Cambrian
boundary: evidence of triploblastic animals
Treptichnus pedum
3D Trace fossils at the Ediacaran-Cambrian
boundary: evidence of triploblastic animals
Treptichnus pedum
Typical 2D
traces made
by diploblasts.
Ediacaran of
Newfoundland
(Mistaken Point Fm.)
A major ice
age, the
Marinoan
(Snowball
Earth)
preceded the
Ediacaran.
How did this
affect animal
evolution?
Equatorial Marinoan diamictites and cap
carbonates in Namibia
Calcite crystal fans
in a Cap
Carbonate grew
out of the sea floor,
indicating high
levels of
atmospheric CO2
had weathered
silicate rocks on
land producing
calcium carbonate
in the oceans.
Alan J. Kaufman
Nature 450, 807-808(6 December 2007)
The Cryogenian Period – Snowball Earth
What role did it play in the evolution of
metazoans?
• The Cryogenian (Greek:
cryos "cold" and genesis
"birth") Period: 850–635
Ma
• Somehow, we went from
this…
• To this… Snowball Earth!