Scientists have been left totally amazed after learning that a 300 million-year-old fossil isn't actually what they originally thought it was.
It turns out there's been a case of mistaken identity. And the reason why they've only just discovered it?
Well, they had it upside down this whole time.
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Oops.
For the last 50 years, scientists believed that a fossil nicknamed 'the blob' belonged to a jellyfish.
This type of fossil is readily found at a site in northern Illinois, called Mazon Creek, which formed 309 million years ago.
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Back in 1979, the fossils were examined by professor Merrill Foster, who determined they were in fact jellyfish fossils, named Essexella Asherae.
However, a new study has revealed that 'the blob' do not belong to jellyfish at all, but something totally different.
Lead author of the study, Roy Plotnick, from the University of Illinois Chicago, explained that he had often looked at the fossils and thought they didn't seem to fit that of a jellyfish.
“I’ve always looked at these jellyfish fossils and I’ve thought, ‘That doesn’t look right to me',” he told Live Science.
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Turns out, the fossils belong to sea anemones instead.
“I said, ‘Wait a minute; that looks like the foot of a sea anemone'.” he added.
Geographic explains that sea anemones are a 'close relative of coral and jellyfish, anemones are stinging polyps that spend most of their time attached to rocks on the sea bottom or on coral reefs'.
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After re-examining the fossils with co-authors James Hagadorn and Graham Young, they discovered that turned upside down, the fossils were clearly anemone.
It seems that the membraneous 'curtain' that's so distinctive on jellyfish, was actually the barrel-shaped body of an anemone.
Added to this, they realised that the 'cap' of the fossil resembled the foot of an anemone.
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“It quickly became obvious that not only it wasn’t a jellyfish, but turned upside down it was clearly an anemone, probably one that burrowed into the seafloor,” Plotnick explained.
“The ‘bell’ was actually an expanded muscular foot used to wiggle the anemone into the seafloor.”
It's now believed that there are actually thousands of sea anemone fossils - mistaken for 'the blob' - that have been incorrectly labelled for decades.
Sea anemone fossils are mega rare (this is because their bodies aren't easily fossilised), so it kind of makes sense that they could have been mistaken so easily.
“Anemones are basically flipped jellyfish. This study demonstrates how a simple shift of a mental image can lead to new ideas and interpretations,” Plotnick added.
Lucy Devine