An object that was discovered in Antarctica in 2011 is now thought to be the egg of a prehistoric sea monster known as a mosasaur.
The huge 11-inch egg was discovered in the icy tundra of Antarctica nearly 10 years ago and - at first glance - you'd be forgiven for thinking that it doesn't look much like an egg at all.
In fact, it looks like a popped rugby ball as much as anything.
However, the geoscientists over at the University of Texas believe that it is a 'soft-shelled' egg that was laid by a mosasaur 66 million years ago.
The mosasaur was a fearsome aquatic lizard that could measure up to 23 feet in length - which is why the egg is pretty big, you'd have to assume.
It was discovered among the rocks by some Chilean scientists at a spot where they also unearthed some bones from mosasaurs and another slightly more famous marine dinosaur, the plesiosaur.
For years it was nicknamed 'The Thing' because the scientists didn't know what it was, but after sitting in a miscellaneous box at the Natural History Museum in Chile for almost a decade, someone finally had an idea.
David Rubilar-Rogers had spent much of that time showing the fossil to anyone who would look, asking if they knew what it could be, but eventually Julia Clarke, a professor at the Jackson's School of Geological Sciences, visited in 2018.
Rubilar-Rogers explained: "I showed it to her and, after a few minutes, Julia told me it could be a deflated egg!"
Lucas Legendre, the lead author of a piece of research done into the egg at the Jackson's School, said: "It is from an animal the size of a large dinosaur, but it is completely unlike a dinosaur egg.
"It is most similar to the eggs of lizards and snakes, but it is from a truly giant relative of these animals."
After microscopes were used to study the specimen, they found several layers of membrane, which indicated that the fossil was really an egg.
It's actually remarkably similar to the see-through quick-hatching eggs that snakes and lizards produce today, but because whatever was inside has obviously left, there's no definite way of telling exactly what laid it.
Dr Legendre added: "Many authors have hypothesised that this was sort of a nursery site with shallow protected water, a cove environment where the young ones [juvenile mosasaurs] would have had a quiet setting to grow up."
The full study of the egg was released in the journal Nature.
Featured Image Credit: Chilean Museum of Natural HistoryTopics: Science, World News, Interesting, Weird