This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Finding a fossilized dinosaur egg is exceptionally rare, but finding a stash of more than 250 shell fragments in the chilly southern reaches of the planet is even more surprising. The discoveries come from southernmost Patagonia in Argentina, where giant, long-necked titanosaurs roamed toward the end of the dinosaur era.
Previous egg discoveries suggested that these massive beasts usually nested much farther north. However, research led by Kohei Tanaka at the University of Tsukuba in Japan, published in the journal Royal Society Open Science, shatters that idea. It shows that titanosaurs nested much farther south than previously known.
"These eggshells provide, to our knowledge, the first indication that titanosaurs nested at relatively high latitudes," the scientists wrote in their paper. The discovery also raises the question of how these giant reptiles kept their eggs warm. The team has some answers for that, too.
The researchers examined 255 fragments collected from the Chorrillo Formation in southernmost Patagonia, Argentina, in 2020 and 2024. Geologists dated the formation to the late Maastrichtian, near the end of the Cretaceous, while microscopic analysis identified the shells as Fusioolithus. This is a type of fossil eggshell that probably belonged to titanosaurs.
At the time, the nesting site lay at around 55 to 60 degrees south, much farther south than most previously known titanosaur nesting sites. Average annual temperatures are estimated to have been around 12°C to 14.5°C (54°F to 58°F). The team analyzed the shape, thickness and pores of the fragments using microscopes and a micro-CT scan.
They compared these features with known dinosaur eggs to try to work out how the nests were built. The dense pore patterns on the eggshells matched those of dinosaur eggs thought to have been buried during incubation. This pore density offers a crucial clue to how these dinosaurs built their nests—and incubated their young.
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