Fossilized dinosaur eggshells unearthed in southern Argentina indicate that giant titanosaurs nested in cool high-latitude environments roughly 70 million years ago, researchers reported. Paleontologists say the porous eggshells suggest these massive animals buried their clutches beneath decaying vegetation to incubate them.
Chorrillo Formation Fossils Push Southern Nesting Limits
Paleontologists working in Santa Cruz province, Argentina, have uncovered more than 250 dinosaur eggshell fragments that extend the known geographic range of titanosaur nesting further south than previously documented. The fossils were recovered from the Chorrillo Formation near El Calafate, a site that dates to the Maastrichtian age of the Cretaceous period roughly 70 million years ago.
During that era, the site sat at an estimated paleolatitude of 55 to 60 degrees south. According to research published in Royal Society Open Science, this makes the location the southernmost confirmed dinosaur egg site in the Southern Hemisphere.
Microscopy and Micro-CT Scans Reveal Burial Incubation
Led by Kohei Tanaka of the University of Tsukuba, the research team examined 255 shell fragments collected across fieldwork in 2020 and 2024. Using microscopy and micro-CT imaging, the scientists analyzed shell thickness, surface ornamentation, and pore structure to understand how the eggs were managed.
The analysis classified the fragments as Fusioolithus, an oogenus commonly associated with titanosaurs, which include some of the largest creatures ever to walk the Earth. Although no complete eggs, embryos, or intact nests were recovered, titanosaur bones and teeth were found within the same formation, supporting the species connection.
The eggshells exhibited high porosity, a characteristic shared with modern animals such as crocodilians and megapode birds that bury their clutches rather than sitting on them. Because titanosaurs were immensely massive, direct brooding was biologically unfeasible.
They’re too big.
Darla Zelenitsky, a paleontologist at the University of Calgary and co-author of the paper
Surviving High-Latitude Paleoclimate Challenges
The high-latitude paleoclimate presented severe reproductive hurdles, including cool seasonal temperatures and extended periods of reduced sunlight. Researchers estimate the average annual temperature at the Magallanodon site was approximately 56 degrees Fahrenheit, with swampy or waterlogged ground conditions.
Without reliable solar radiation for warmth at such high latitudes, the scientists concluded that the animals relied on alternative thermal sources. The eggs, as shown by a high eggshell porosity, would have been incubated in nests buried by nesting materials and would have used the heat generated by decaying vegetation, according to the study authors.
Similar nesting strategies have been inferred for non-brooding dinosaurs in high-northern paleolatitudes, where hadrosaur and theropod remains have been studied in Siberia, Alaska, and Alberta, Canada. However, physical evidence from high southern latitudes has remained scarce due to a lack of definitive eggshell discoveries in Antarctica and Australia.
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