The mysterious Antarctic egg might belong to an extinct sea lizard

The mysterious Antarctic egg might belong to an extinct sea lizard

In 2011, Chilean researchers discovered a strange, fossilized object in Antarctica. It was the most like a deflated football and they couldn’t bring it home. For years, the object – nicknamed ‘The Thing’, was dusted in the Chilean National Museum of Natural History. But now researchers at the University of Texas (Austin) have looked at the object again and they have to conclude that it is a 66 million-year-old egg that originally had a soft eggshell (as well as the eggs of turtles that have).

The fossilized egg. 
Image: Legendre et al. (2020).

What exactly was in the egg is not certain. Because the organism in question has crawled out before the egg fossilized. But based on the sheer size of the egg, the researchers think of the pup of a huge marine reptile, such as a mosasaur. “It’s from an animal the size of a large dinosaur, but it doesn’t look like a dinosaur in any way,” said researcher Lucas Legendre. “It looks more like the eggs of lizards and snakes, but then it is a truly gigantic relative of these animals.”

After ‘The Thing’ had been mysterious in the museum for years, the big breakthrough came in 2018. Geologist Julia Clarke visited the museum and immediately suspected it might be an egg. To confirm the hypothesis, a comprehensive analysis of the egg followed. And in doing so, several layers of membranes have been encountered that confirm that it was an egg. The structure of the egg appears to be very similar to that of transparent and rapidly hatching eggs that some snakes and lizards lay today.

In order to get a slightly better grip on what had been in the egg, the researchers decided to compare the body size of 259 reptiles that live on Earth today with the size of their eggs. And judging by those proportions, they estimate that the reptile that laid ‘The Thing’ was more than 6 meters long (excluding tail). It must therefore almost be a marine reptile. This hypothesis is further endorsed for the fact that in the area where the egg was found, quite a few skeletons of both adult and newborn mosasauruses and plesiosaurs have also been found. “Many scientists suspect that this was a kind of nursery, with shallow water and creeks, an environment where the young could grow up peacefully,” legendre said.

The suggestion that large marine reptiles, such as mosasauruses, laid this egg, is quite revolutionary. Because it is generally assumed that these animals did not lay eggs at all, but were live-giving. Ideas about exactly how the marine reptiles laid eggs are still in their infancy. They may have just done it in open water (just like sea snakes do). Or they laid their eggs – like turtles – on the beach, after which the young made their way to the water. The latter scenario requires quite a lot from the mothers, who were far too heavy to be able to carry their body weight on land. It is possible that they kept their bodies in the water and only threw their tails on land. “We can’t rule it out,” Clarke said. “Because nothing like this has ever been discovered.” And so ‘The Thing’ still loves its mysterious character.


” Egg from Antarctica’s Big and Might Belong to an Extinct Sea Lizard ” – University of Texas, Austin