How Giant Titanosaurs Kept Their Eggs Warm in Cold Climates

Unearthing Titanosaur Nests in Southern Argentina

Researchers discovered 255 eggshell fragments across two field seasons in 2020 and 2024 at the Chorrillo Formation, located 322 kilometers north of the Strait of Magellan. The site dates back to the Late Cretaceous period, between 72 and 66 million years ago, just before the extinction event that wiped out the dinosaurs. At the time, the location sat at a latitude between 55 degrees and 60 degrees south, featuring a climate comparable to modern-day New York City, as noted by University of Calgary paleontologist Darla Zelenitsky. The eggshells belong to titanosaurs, a group of four-legged, long-necked, and long-tailed herbivores that weighed up to 75 tonnes, roughly half the mass of a blue whale. While titanosaur bones have turned up in locations as varied as Antarctica, Mongolia, and Texas, finding their nests at such high latitudes changes what scientists understand about the reproductive capabilities of these giant reptiles. University of Edinburgh professor of paleontology and evolution Steve Brusatte, who was not involved in the research, said that the discovery highlights the adaptability and resiliency of some of the largest animals in Earth’s history.

Solving the High-Latitude Incubation Problem

Because adult titanosaurs reached immense proportions, they could not brood their eggs the way modern birds do. As Darla Zelenitsky explained, They’re too big. The nest would be one big omelette. Instead, the research team analyzed microscopic pores on the eggshells to deduce their incubation method. The structural analysis indicated that the eggs required a humid environment to prevent them from drying out in the open air. To solve the challenge of lower temperatures and shorter sunlight hours at high latitudes, the sauropods adopted a strategy similar to modern crocodiles and megapode birds. According to the study led by University of Tsukuba paleontologist Kohei Tanaka, the titanosaurs buried their eggs in mound nests constructed from soil and rotting vegetation. Microbes breaking down the plant material generated the steady heat required for the embryos to develop and hatch over periods lasting many months.

Year-Round Residence Versus Seasonal Migration

The discovery of a high-latitude nesting ground also fuels an ongoing debate regarding whether giant sauropods migrated long distances or remained in cooler regions year-round. Previously, paleobiologists assumed that sauropods visited high latitudes only during warm summers before migrating back toward the equator for the winter. However, University College London professor of paleobiology Paul Upchurch said that the presence of fossilized eggs changes that interpretation. 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, Upchurch said. The Chorrillo Formation ecosystem supported a diverse array of fauna alongside the massive titanosaur Nullotitan glaciaris, which reached lengths of up to 25 meters. Fossil records show that these plant-eaters shared their coastal plain habitat with the smaller herbivore Isasicursor santacrucensis, megaraptors, crocodiles, turtles, frogs, birds, and mammals, painting a picture of a thriving, resilient polar-adjacent biome just prior to the end of the Cretaceous.