Petrified Chains of "Poop" Turn Out to Be One of Earth's Oldest Skeletons
Palaeopascichnus linearis is among the world's oldest skeletal creatures, according to new research published in the October issue of the journal Precambrian Research.
These tiny globular, ocean bottom-dwellers may have been amoeba-like
creatures that accrued bits of sand and sediment around themselves to
create their own exoskeleton. All earlier organisms with similar exoskeletons
were much, much smaller, said study leader Anton Kolesnikov, a
paleontologist at the Institute of Petroleum Geology and Geophysics at
the Siberian Branch of the Russian Academy of Sciences and the
University of Lille in France. [In Images: The Oldest Fossils on Earth]
"It is the oldest known macroscopic skeletal organism," Kolesnikov said of P. linearis.
Mystery fossils
Palaeopascichnus fossils are found the world over in rocks from the Ediacaran period,
which spanned from 635 million to 541 million years ago. No one had
been able to agree on exactly what the fossils were, though, Kolesnikov
wrote in an email to Live Science. Some thought they were trace fossils
left behind by some organism shuffling along the seafloor. Others
suspected they were coprolites — fossilized poop. Still others argued
they were organisms in and of themselves.
Figuring out the answer was difficult because many areas where
Ediacaran fossils are found around the world are protected, Kolesnikov
said. But in the Olenek Uplift of northeastern Siberia, past the Arctic
Circle, Kolesnikov and his colleagues discovered sites where they
collected more than 300 new specimens of the fossils. They also
discovered more fossils from the area in collections dating back to the
1980s.
"Huge amounts of fossils from Siberia allowed us to experiment with
thin sampling, sectioning, cutting, studying in [electron] microscopes"
and more, Kolesnikov said.
DIY skeletons
This analysis revealed that the fossils were made up of chains of
between two and 40 spherical or oval modules, each between 0.04 inches
and 0.2 inches (1 and 5 millimeters) in diameter. Each module was
bordered by a fine rim of sediment.
More than anything, the researchers reported, the fossils looked like
today's xenophyophores, which are giant foraminifera. These bizarre
creatures are amoebas that protect themselves with "agglutinated tests,"
or exoskeletons of sediment they cement to themselves with their own
excretions. Scientists reporting in a March 2018 paper in the Zoological Journal detailed the discovery of a new species of these xenophyophores, Aschemonella monile, which look remarkably similar to the fossil versions from Siberia.
Original article on Live Science.
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