About 68 million years ago, a remarkable fossil egg was found in Antarctica. This egg, dubbed “The Thing,” belonged to a gigantic marine reptile thought to have laid eggs rather than giving birth to live young, which was the common belief for such creatures.
Discovered on Seymour Island, the egg measures about 11 inches long and 8 inches wide, making it the largest soft-shelled egg ever identified and the second-largest egg of any known animal. Initially, this fossil didn’t even look like an egg; it appeared more like a deflated bag, hidden in Antarctic sediment.
Using a microscope, researchers uncovered its fragile shell, just a fraction of a millimeter thick, with a texture similar to modern lizard or snake eggs, rather than the thick shells typical of dinosaur eggs. Lucas Legendre, a paleontologist at the University of Texas at Austin and leader of the research team, emphasized the importance of this find in understanding the evolution of reptile reproduction.
The egg, scientifically named Antarcticoolithus bradyi, provides intriguing clues about how massive marine reptiles like mosasaurs presumably reproduced. Prior studies suggested that these creatures gave birth to live young far from shore. However, this egg suggests a different reproductive strategy: laying soft-shelled eggs in water that allowed the young to hatch almost immediately.
Interestingly, close to the egg’s site, bones of Kaikaifilu hervei, a large mosasaur, were found. This species could reach about 33 feet, making it a strong candidate for the egg’s parent, given that the estimated parent size fits well within this range.
Most fossilized eggs discovered so far had hard, mineral-rich shells, leading scientists to believe that these were the norm. Recent analysis has started to shift this perspective, suggesting that soft-shelled eggs may have been common in ancient reptiles. This Antarctic egg adds to our understanding by showing that even large marine reptiles had soft-shelled eggs, possibly adapted to their environment around the ancient South Pole.
Research has revealed that soft eggs rarely fossilize, as they deteriorate quickly. However, the conditions in Antarctica at that time were likely ideal for preservation, with layers of mud and sand protecting the egg from decay.
This discovery shines a light on the complex life cycles of ancient reptiles, helping us piece together how they thrived in colder, seasonal climates. The study is detailed in Nature.
By revealing new insights into the reproductive habits of ancient marine reptiles, this discovery reshapes the narrative of how these creatures lived and evolved.
