Titanosaur Eggs Discovered at Record Southern Latitude

Researchers uncovered 255 eggshell fragments in the Chorrillo Formation of southern Argentina, about 200 miles (322 km) north of the Strait of Magellan. The material dates to roughly 68 million years ago, when the site lay between 55° S and 60° S. The fragments represent the highest-latitude nesting environment known for sauropods and the southernmost definitive dinosaur eggs. The eggshells are highly porous, a trait that would have caused rapid water loss if left exposed.

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Because titanosaurs were too large to brood their clutches, the study proposes they built mound nests of vegetation and soil. Heat from decaying plant matter would have provided incubation warmth, while the surrounding material retained moisture to protect the porous eggs. The nests are estimated to have been the size of a picnic table, creating a noticeable mound in the landscape. Individual eggs were tiny—about 1/18,000 the size of an adult titanosaurs—and could have held roughly 4 liters of liquid, producing hatchlings weighing around 4 kg (?9 lb).

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Titanosaurs, some weighing up to 75,000 kg, are now known to have reproduced at high latitudes, demonstrating greater ecological flexibility than previously recognized. The presence of eggs suggests these giants either remained in the region year-round or timed their reproductive cycle to the brief warm season, challenging earlier assumptions that they migrated only during summer months. Abundant food resources would have been necessary for hatchlings to achieve the massive adult sizes characteristic of the group.

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Paleontologist Darla Zelenitsky of the University of Calgary highlighted the novelty of confirming high-latitude nesting and emphasized the likely use of mound nests to generate incubation heat. Steve Brusatte, a professor of paleontology at the University of Edinburgh, noted that the eggs belong to titanosaurs, a group of large, long-necked herbivores. Paul Upchurch of University College London argued that the find shows titanosaurs could have stayed in these regions all year or at least completed their reproductive cycle during the warm part of the year. Fossil teeth from the site suggest the eggs may belong to colossosaurian titanosaurs, among the largest members of the clade.

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• “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,” — Darla Zelenitsky, University of Calgary

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• “They clearly spent time in higher latitude areas, but until now it wasn’t known whether they were also nesting there,” — Darla Zelenitsky, University of Calgary

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• “The most likely scenario is that these titanosaurs laid their eggs in mound nests made of vegetation and soil, where incubation heat came mostly from rotting plant material,” — Darla Zelenitsky, University of Calgary

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• “Some of the very largest animals in Earth’s history were laying eggs and hatching their babies at high latitudes in the Cretaceous, which is a new fact about dinosaur biology and behaviour that makes us better appreciate their adaptability and resiliency.” — Paul Upchurch, University College London

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• “Now that we have eggs from a high latitude, this suggests that they might have stayed there all year, or at least were able to go through their reproductive cycle during the warm part of the year at those high latitudes,” — Paul Upchurch, University College London

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• “I envision the nest as a picnic table size mound of dirt and vegetation with the egg clutch buried inside … so it probably wasn’t an inconspicuous structure,” — Darla Zelenitsky, University of Calgary

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