Case cracked: Mystery Antarctica fossil a huge prehistoric egg

Scientists had nicknamed it “The Thing ”— a mysterious football-sized fossil discovered in Antarctica that sat in a Chilean museum awaiting someone who could work out just what it was.

Now, analysis has revealed that the mystery fossil is in fact a soft-shelled egg, the largest ever found, laid about 68-million years ago, possibly by a type of extinct sea snake or lizard.

The revelation ends nearly a decade of speculation about the fossil, and could change thinking about the lives of marine creatures in this era, Lucas Legendre, lead author of a paper detailing the findings, published in the journal Nature, said.

“It is very rare to find fossil soft-shelled eggs that are that well-preserved,” Legendre, a postdoctoral fellow at the University of Texas at Austin, said.

“This new egg is by far the largest soft-shelled egg ever discovered.

“We did not know that these eggs could reach such an enormous size, and since we hypothesise it was laid by a giant marine reptile, it might also be a unique glimpse into the reproductive strategy of these animals,” he said.

The fossil was discovered in 2011 by a group of Chilean scientists working in Antarctica.

It looks a bit like a crumpled baked potato but measures a whopping 28cm by 18cm.

For years, visiting scientists examined the fossil in vain, until in 2018 a paleontologist suggested it might be an egg.

It wasn’t the most obvious hypothesis given its size and appearance, and there was no skeleton inside to confirm it.

Analysis of sections of the fossil revealed “a layered structure similar to a soft membrane, and a much thinner hard outer layer, suggesting it was softshelled,” Legendre said.

“This was also confirmed by chemical analyses, which showed that the eggshell is distinct from the sediment around it, and was originally a living tissue.”

But that left other mysteries to unravel, including what animal laid such an enormous egg — only one bigger has been found, produced by the nowextinct elephant bird from Madagascar.