A mysterious fossil is definitely a large, soft-shell egg from about 66 million years in the past, researchers report.

In 2011, Chilean scientists found a mysterious fossil in Antarctica that regarded like a deflated soccer. For almost a decade, the specimen sat unlabeled and unstudied within the collections of Chile’s Nationwide Museum of Pure Historical past. Scientists recognized it solely by its sci-fi movie-inspired nickname, “The Thing

“It’s most much like the eggs of lizards and snakes, however it’s from a really large relative of those animals.”

Measuring in at greater than 11 by 7 inches, the egg is the biggest soft-shell egg ever found and the second-largest egg of any identified animal.

The specimen is the primary fossil egg present in Antarctica and pushes the bounds of how huge scientists thought soft-shell eggs may develop. Other than its astounding dimension, the fossil is critical as a result of scientists suppose it was laid by an extinct, large marine reptile, reminiscent of a mosasaur. It’s a discovery that challenges the prevailing thought that such creatures didn’t lay eggs.

The fossilized egg is brown and looks almost deflated A aspect view of the fossil of the large egg. (Credit score: Legendre et al.)

“It’s from an animal the dimensions of a giant dinosaur, however it’s fully in contrast to a dinosaur egg,” says lead writer Lucas Legendre, a postdoctoral researcher on the Jackson Faculty of Geosciences at The College of Texas at Austin. “It’s most much like the eggs of lizards and snakes, however it’s from a really large relative of those animals.”

Coauthor David Rubilar-Rogers of Chile’s Nationwide Museum of Pure Historical past was one of many scientists who found the fossil in 2011. He confirmed it to each geologist who got here to the museum, hoping anyone had an thought, however he didn’t discover anybody till Julia Clarke, a professor within the Jackson Faculty’s geological sciences division, visited in 2018.

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“I confirmed it to her and, after a couple of minutes, Julia advised me it might be a deflated egg!” Rubilar-Rogers says.

The Mosasaur is a long lizard with dark brown and black markings on its back. The egg and hatchling are tiny compared to the lizard, which is at least 20 feet long An artist;s interpretation of a mosasaur, an extinct marine reptile that scientists suppose might have laid the egg. An grownup mosasaur is proven subsequent to the egg and a hatchling. (Credit score: Francisco Hueichaleo)

Utilizing a set of microscopes to review samples, Legendre discovered a number of layers of membrane that confirmed that the fossil was certainly an egg. The construction is similar to clear, quick-hatching, eggs laid by some snakes and lizards as we speak, he says. Nevertheless, as a result of the fossil egg is hatched and comprises no skeleton, Legendre had to make use of different means to zero in on the kind of reptile that laid it.

He compiled an information set to check the physique dimension of 259 residing reptiles to the dimensions of their eggs, and he discovered that the reptile that laid the egg would have been greater than 20 ft lengthy from the tip of its snout to the tip of its physique, not counting a tail. In each dimension and residing reptile relations, an historical marine reptile matches the invoice.

A drawing of the massive mosasaur laying an egg underwater from which a baby is emerging An artist’s interpretation of a child mosasaur rising from an egg. (Credit score: John Maisano/Jackson Faculty of Geosciences)

Including to that proof, the rock formation the place the egg was found additionally hosts skeletons from child mosasaurs and plesiosaurs, together with grownup specimens.

“Many authors have hypothesized that this was type of a nursery website with shallow protected water, a cove atmosphere the place the younger ones would have had a quiet setting to develop up,” Legendre says.

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“We are able to’t exclude the concept they shoved their tail find yourself on shore as a result of nothing like this has ever been found.”

The paper doesn’t focus on how the traditional reptile may need laid the eggs. However the researchers have two competing concepts.

One includes the egg hatching within the open water, which is how some species of sea snakes give delivery. The opposite includes the reptile depositing the eggs on a seashore and hatchlings scuttling into the ocean like child sea turtles.

The researchers say that this could demand some fancy maneuvering by the mom as a result of large marine reptiles had been too heavy to assist their physique weight on land. Laying the eggs would require the reptile to wriggle its tail on shore whereas staying largely submerged, and supported, by water.

“We are able to’t exclude the concept they shoved their tail find yourself on shore as a result of nothing like this has ever been found,” Clarke says.

The examine seems in Nature. Further coauthors are from the College of Chile and UT Austin. The Howard Hughes Medical Institute’s Science Training Program and the Nationwide Analysis and Improvement Company of Chile funded the analysis.

Supply: UT Austin