Back in 2011, Chilean scientists discovered a mysterious fossil in Antarctica that looked like a deflated football. For nearly a decade, the specimen sat unlabelled and unstudied in the collections of Chile’s National Museum of Natural History, with scientists identifying it only by its sci-fi movie-inspired nickname – “The Thing”.

An analysis led by researchers at The University of Texas at Austin has finally revealed that the fossil is in fact a giant, soft-shell egg dating from about 66 million years ago. Measuring just over 28x18cm (11x7in), it is the largest soft-shell egg ever discovered and the secondlargest egg of any known animal.

The likely candidate

In addition, this specimen is the first fossil egg found in Antarctica (although back then, the region had a warm climate) and it pushes up the limits of how big scientists thought soft-shell eggs could grow. Aside from its astounding size, however, the fossil is also significant because scientists think it was laid by an extinct, giant marine reptile, such as a mosasaur — a discovery that challenges the prevailing thought that such creatures did not lay eggs.