Researchers say they have determined a mystery fossil discovered in Antarctica in 2011 is a large egg, possibly laid by an ancient aquatic reptile.
Science publication Inverse reports that since the fossil was discovered, researchers referred to it as the "thing," because they could not classify it. They compared it to a deflated American football — oval in shape, about 28 centimeters long and 18 centimeters wide.
In a study published Wednesday in the science journal Nature, researchers from the University of Texas at Austin used microscopic analysis to confirm that the fossil is indeed an ancient egg.
They analyzed the body size of 260 living reptiles, compared them with their egg sizes, and estimated that the animal that laid the mystery egg would have been roughly 7 meters long.
They also determined the fossil egg was soft-shelled, unlike dinosaur eggs, and similar to turtle eggs — suggesting an aquatic species. The researchers found no trace of what was in the egg, but the fossil was found in a formation in Antarctica rock formation that also contained fossils from mosasaurs — huge ancient aquatic reptiles.
If the fossil is determined to be a mosasaur egg, the new finding would be significant, as scientists previously did not believe the ancient creatures laid eggs.
Since there are no living aquatic reptiles the size of a mosasaur, the egg seems to be in a class of its own.