Some of the largest dinosaurs ever to walk the planet may have solved a delicate problem — keeping their eggs warm without crushing them — in a cold place.
Broken eggshells from southern Patagonia are giving researchers novel clues about how giant titanosaurs may have nested near the end of the Cretaceous period, Earth.com reported.
Here's what to know
Researchers say titanosaurs that nested in what is now southern Argentina probably buried their eggs, perhaps in covered nests that helped them incubate in the cool, high-latitude setting.
The fossils came from the Chorrillo Formation near El Calafate — and mark nesting at about 55 to 60 degrees south — making it the Southern Hemisphere's southernmost confirmed dinosaur egg site, Earth.com noted.
Kohei Tanaka of the University of Tsukuba led the study, which examined 255 eggshell fragments collected in 2020 and 2024 from the Magallanodon site.
The site may have been swampy or waterlogged, and the average annual temperature there is estimated at 56 degrees Fahrenheit, the outlet stated.
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Researchers classified the shells as Fusioolithus, a fossil egg type commonly associated with titanosaurs. Though they found no embryos to identify the species, they located titanosaur bones and teeth from the same formation.
The shells' pore structure most closely resembled eggs from animals that incubate in covered nests rather than eggs left exposed.
More background
Because titanosaurs were so massive, they probably could not brood their eggs like modern birds without crushing them.
"They're too big. The nest would be one big omelet," Darla Zelenitsky, a paleontologist at the University of Calgary and co-author of the paper, said, per Earth.com.
Researchers estimated that eggs of this type were 4.3 to 9.1 inches across and 1.6 to 14.7 pounds. Even without a complete egg from the site, the shells remained highly porous across that full estimated size range.
That suggests eggs were buried under nesting material. Living crocodilians and some birds use covered nests that get heat from sunlight, the ground, or decaying plant matter, Earth.com stated.
For this Patagonian site, the authors consider decomposing vegetation a plausible heat source.
Sunlight would have been less dependable at such a high latitude, where daylight shifts sharply with the seasons.
What's being done?
The team measured all 255 shell fragments, examined selected pieces with microscopes, and used micro-CT imaging to view the inside of one fragment in three dimensions.
The researchers also compared the shells with the global record of Fusioolithus nesting sites. That comparison helped show that the Chorrillo eggs were notable not just for their location but also for what they suggest about how giant dinosaurs adapted to cold environments.
Scientists have yet to find a complete egg, an intact nest, or embryos, so they still cannot pin down clutch size, nest form, or the titanosaur species.
"Even these absolute largest dinosaurs figured out a way to not only reproduce or nest in the lower latitude environments but also in these higher-latitude environments, which are usually more challenging," Zelenitsky observed, per Earth.com.
Where can I learn more?
These articles look at a titanosaur fossil from Antarctica, extinction-era rocks, a Brazilian pterosaur, and a Spanish stegosaur skull.
• In Antarctica, a fossil once dismissed as ordinary became the continent's first dinosaur bone.
• Ancient rocks suggest dinosaurs faced a hidden ecological crisis before the asteroid aftermath.
• In Brazil, a 113 million-year-old pterosaur preserved molecules revealing a fish-and-squid diet.
• In Spain, the best-preserved stegosaur skull in Europe could reshape dinosaur migration maps.
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