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The fossil on
the left is quite large, approximately 3 centimeters across and 9 centimeters
long, while the fossil on the right is roughly 1.5 centimeters across and 2.5
to 3 centimeters long.
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Kimberella,
one of the most fascinating Vendian fossils, has received a great deal of
attention lately. It was hypothesized to be a box jellyfish (cubozoan) until
new information came to light. The original interpretation was based on a
small number of specimens from South Australia that looked like four-parted
box jellyfishes lying on their sides. Recently, many well-preserved and large
(up to 3 centimeters across!) specimens from the White Sea region of Russia
were found by teams of researchers from the Paleontological Institute of the
Russian Academy of Sciences in Moscow (PIN) and UCMP.
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Fedonkin and
Waggoner have shown that Kimberella was a bilaterally symmetric animal
that had rigid parts. Specimens of Kimberella from the White Sea are
found as relatively deep depressions on the undersides of siltstone slabs.
Fedonkin and Waggoner reasoned that Kimberella probably had a tough
shell-like covering that rigidly stood up into the sediment when the animals
were buried. Thus, Kimberella appears to be somewhat like a mollusc.
Nevertheless, it is still uncertain which group of modern animals is most
closely related to this interesting animal.
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