To Researchers’ Surprise, This Giant Dinosaur Laid Eggs in a Cold Climate

A new study suggests that titanosaurs used rotting vegetation to keep their eggs warm much like crocodiles do today

Sara Hashemi | Daily Correspondent

September 9, 2026 4:29 p.m.

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Millions of years ago, during the late Cretaceous, some of the largest dinosaurs ever were laying eggs in surprisingly cold places.

Looking at fossilized titanosaur eggs found in southern Argentina’s Chorrillo Formation, a study published in the journal Royal Society Open Science today offers a new understanding of how dinosaurs survived and reproduced so far from the equator.

Titanosaurs belonged to a group of long-necked and four-legged dinosaurs called sauropods. Adults could weigh up to 75 tonnes—over eight times bigger than a Tyrannosaurus rex and 12 times as heavy as an elephant.

“We know their bones have turned up in places as far south as Antarctica and southern Argentina, and as far north as Mongolia and Texas,” says Darla Zelenitsky, a study co-author and paleontologist at the University of Calgary in Canada, to Katie Hunt at CNN. “They clearly spent time in higher latitude areas, but until now it wasn’t known whether they were also nesting there.”

The 255 egg fragments at the center of the discovery were uncovered in 2020 and 2024 in the Chorrillo Formation, a rock formation on the southern tip of Argentina. They date back to about 68 million years ago, when the site, sitting at between 55 degrees and 60 degrees south latitude, had a climate comparable to New York City today, Zelenitsky tells Emily Chung at the Canadian Broadcasting Corporation.

Zelenitsky and her colleagues then took a closer look at the pores on the eggshells using microscopes and micro-CT scanners. “Their eggshells were very porous, which means if the eggs were left out in the open, they would lose water, dry out, and the embryos would die,” Zelenitsky explains to CNN.

This suggests the giant creatures incubated their eggs using a technique shared by modern crocodiles—using piles of rotting vegetation for heat. “Buried in sand, soil, or vegetation, the nest would stay humid or damp enough for the eggs to survive,” says Zelenitsky.

Robert Reisz, a paleontologist at the University of Toronto who was not involved in the study, tells Ivan Semeniuk at the Globe and Mail that the study provides new insight on the dinosaurs' reproductive strategies. “That titanosaurs laid eggs at such high latitudes is inherently interesting, especially since the evidence points to mound incubation by plant decay as the main source of heat for these animals,” he says.

The research highlights how dinosaurs adapted to environmental conditions, says Zelenitsky to the CBC. It’s usually harder for such large animals to find the resources needed to survive and reproduce in such a climate. Still, they found 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."

The researchers still don’t know what species of titanosaur the eggs belonged to, but teeth also found at the site belonged to colossosaurian titanosaurs. While there is no direct association between the eggshells and skeletal remains, the authors note in the study, it’s possible they could belong to the same species.

“If these eggshells belong to colossosaurians, the hatchlings had to have had plenty of nutritious food resources in that environment to start packing on the tonnes to eventually reach their colossal body sizes,” Zelenitsky tells CNN.

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.