A new study describes a record-breaking sauropod nesting site: scientists discovered over 250 eggshell fragments in the Chorrillo Formation in Patagonia. These fossils were found far to the south—approximately 300 kilometers north of the Strait of Magellan—in a region estimated to have been located between 55° and 60° South latitude about 68 million years ago. The study’s findings have been published in the journal Royal Society Open Science.
Dating back to the Late Cretaceous period, this site represents the highest-latitude area containing egg remains in the Southern Hemisphere. It is also the highest-latitude sauropod nesting site known worldwide and provides the first evidence that titanosaurs nested at relatively high latitudes.
The high porosity of the eggshells—a common feature of titanosaur eggs—suggests they were completely covered during incubation. So, what kind of incubator do you use if you are one of the largest dinosaurs to ever walk the Earth? As study author Darla Zelenitsky explained, the options are limited.
“Birds can nest at high latitudes because they warm their eggs with their own body heat, but if titanosaurs had incubated their eggs like birds, the nest would essentially have turned into one giant omelet, so that seems unlikely,” she said. “I also don’t think sunlight alone would have provided enough warmth for these eggs given the Late Cretaceous conditions in a region located not far from where the Drake Passage is today.” Instead, it appears these high-latitude sauropods employed a type of incubation similar to that attributed to large hadrosaurs (duck-billed dinosaurs)—whose eggs have also been found at high latitudes, albeit in the Northern Hemisphere. This method harnesses the heat generated by decomposition, utilizing mounds of rotting vegetation.
As the vegetation decomposed, it generated heat, much like a compost pile. This warmth could sustain embryonic development throughout the incubation period and, according to Zelenitsky, offers the most plausible explanation for how dinosaurs managed to nest in the cool conditions of high paleolatitudes.
The eggshell fossils have been assigned to the oogenus Fusioolithus. This is not the name of a specific animal, but rather a designation for eggs laid by a species of titanosaur.
Although these titanosaurs shared similar nesting habits, they differed significantly from hadrosaurs. Weighing in at around 75,000 kilograms—roughly five times heavier—this group includes giants such as Argentinosaurus and Patagotitan. It is incredible, Zelenitsky notes, to imagine such giants inhabiting these latitudes.
“It amazes me that such enormous dinosaurs could nest so far from the equator,” she said. “Since egg-laying reptiles that do not brood their young typically struggle to nest at high latitudes, it is incredible to realize that the largest dinosaurs not only lived there but also hatched their young there.” This discovery points to behavioral reproductive plasticity in these dinosaurs, as other titanosaurs of the same period nested at lower latitudes and relied on solar radiation for egg incubation—much like modern sea turtles do.
This finding expands the map of known titanosaur nesting sites and raises intriguing questions about how Earth’s ancient giants adapted to the cold in their environment.
About the Author
