550 Million Year Old Fossils Reveal New Insight into Fossil Formation

Some 550 million year old fossils may be telling researchers a bit more about the process of fossil formation in general. The new discoveries could allow scientists to interpret fossils in a new way, learning a bit more about the ancient creatures that they represent.

In this case, the researchers studied a fossil animal from the Ediacaran Period, called Conotubus. This creature's fossils are usually associated with pyrite, which is commonly called fool's gold. Conotubus was tube-shaped, and scientists believe that it probably was composed of substances similar in hardness to human fingernails. The fossilized tubes, though, are all that remain of the soft-bodied animals that probably inhabited them.

"The vast majority of the fossil record is composed of bones and shells," said James Schiffbauer, one of the researchers, in a news release. "Fossils of soft-bodied animals like worms and jellyfish, however, provide our only views onto the early evolution of animal life. Most hypotheses as to the preservation of these soft tissues focus on passive processes, where normal decay is halted or impeded in some way, such as by sealing off the sediments where the animal is buried. Our team is instead detailing a scenario where the actual decay helped 'feed' the process turning the organisms into fossils-in this case, the decay of the organisms played an active role in creating fossils."

The researchers analyzed the fossils to determine what caused the pyrite to form. In the end, they found that it formed on the organisms' outer tube when bacteria first began consuming the animal's soft tissues; the decay actually promoted the formation of the pyrite.

"Normally, the earth is good at cleaning up after itself," said Schiffbauer. "In this case, the bacteria that helped break down these organisms also are responsible for preserving them as fossils. As the decay occurred, pyrite began replacing and filling in space within the animal's exoskeleton, preserving them. Additionally, we found that this process happened in the space of a few years, perhaps even as low as 12 to 800. Ultimately, these new findings will help scientists to gain a better grasp of why these fossils are preserved, and what features represent the fossilization process versus original biology, so we can better reconstruct the evolutionary tree of life."

The findings are published in the journal Nature Communications.

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