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Titanosaur Eggs Reveal Ancient Burial Incubation in Cool Southern Argentina
9/9/2026, 9:18:48 PM
New Study Sheds Light on Nesting Strategy
A collaborative team led by University of Tsukuba paleontologist Kohei Tanaka and University of Calgary paleontologist Darla Zelenitsky published a paper in *Royal Society Open Science* describing how the massive titanosaurs that roamed the Late Cretaceous (72–66 million years ago) kept their large, volleyball-sized eggs warm. By examining electron-microscope images of the porous shells, the researchers concluded that the embryos were likely incubated in buried nests, a method comparable to that of modern crocodiles and megapodes, which rely on heat generated by decomposing vegetation.
Background: Size, Eggs, and Climate
Titanosaurs such as *Nullotitan glaciaris* could reach lengths of 25 metres and weigh up to 75 tonnes—about half the mass of a blue whale. Their eggs, classified as *Fusioolithus*, have been found in dozens of sites closer to the equator, but the recent discovery of shell fragments in the Chorrillo Formation near the southern tip of Argentina places them at a latitude comparable to Red Deer, Alberta, with a climate similar to present-day New York City. In such a cool environment, direct solar heating or body-heat brooding would have been ineffective.
Microscopic Evidence Points to Burial
The study measured the density and size of microscopic pores on the eggshells. The shells were found to be highly porous, a trait that facilitates gas exchange when eggs are buried in moist, decomposing plant matter. Zelenitsky noted that less-porous shells are typical of eggs exposed to open air, whereas the titanosaur shells’ porosity aligns with burial incubation. This pattern mirrors the nesting behavior of crocodiles, which bury their eggs in warm piles of rotting vegetation.
Implications for Dinosaur Adaptability
Zelenitsky argued that the ability to employ diverse nesting strategies likely contributed to titanosaurs’ global success during the Late Cretaceous. The discovery expands the known geographic range of burial incubation beyond tropical regions and suggests that large herbivorous dinosaurs could thrive in a wider array of climates than previously assumed.
Future Research Directions
The authors recommend broader surveys of titanosaur nesting sites worldwide, including comparisons with eggs from Spain that exhibit thinner, less porous shells indicative of open nests. Such work could clarify whether nesting flexibility was a key factor in the group’s worldwide dispersal.
