Fossil unearthed in Antarctica is an egg laid by a prehistoric sea monster

An object found in Antarctica in 2011 has finally been confirmed as the egg from a prehistoric sea monster.

The 11-inch egg looks like a deflated American football and is completely unlike any other known dinosaur egg. It’s a ‘soft-shelled’ egg according to geoscientists from the University of Texas and came from a gigantic sea lizard known as a mosasaur.

In the case of this egg, it’s believed to have been laid by a mosasaur measuring up to 23 feet around 66 million years ago.

The egg was found by Chilean scientists amongst rocks containing skeletons of mosasaurs and other ancient marine creatures known as plesiosaurs.

Experts were so unsure what to make of it, they nicknamed the egg ‘The Thing’ after the sci-fi movie because of its mysterious origins.

It lay in an unlabelled collection in Chile’s National Museum of Natural History for almost a decade.

David Rubilar-Rogers from the museum was one of the scientists who discovered the fossil in 2011. He showed it to every geologist who came to the museum, hoping somebody had an idea, but he didn’t find anyone until Julia Clarke, a professor in the Jackson School’s Department of Geological Sciences, visited in 2018.

‘I showed it to her and, after a few minutes, Julia told me it could be a deflated egg!’ Rubilar-Rogers said.

Using a suite of microscopes to study samples, Lucas Legendre – a post-doctoral fellow at the University of Texas found several layers of membrane that confirmed that the fossil was indeed an egg.

The structure is very similar to transparent, quick-hatching, eggs laid by some snakes and lizards, he said.

‘It is very rare to find fossil soft-shelled eggs that are that well-preserved,’ Legendre told the AFP news agency.

‘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.’

The University of Texas team don’t go into the specifics of how the ancient sea monster laid the egg in their study, but there are two competing ideas.

One involves the egg hatching in the open water, which is how some species of sea snakes give birth. The other involves the reptile depositing the eggs on a beach and hatchlings scuttling into the ocean like baby sea turtles.

The researchers say that this would require some fancy maneuvering by the mother because giant marine reptiles were too heavy to support their body weight on land. Laying the eggs would require the reptile to wriggle its tail on shore while staying mostly submerged, and supported, by water.

‘We can’t exclude the idea that they shoved their tail end up on shore because nothing like this has ever been discovered,’ Clarke said.