Dinosaur eggshells unearthed Patagonia belong to unexpected giant species, say experts | Discover Wildlife

Researchers have analysed dinosaur eggshells collected from southern Patagonia and discovered they likely belong to a rather unexpected dinosaur. The finding has been described in the journal Royal Society Open Science.

The eggshells were collected from the Chorrillo Formation, which dates to the latest Cretaceous period around 66-69 million years ago. Analysis of their microstructure revealed that all specimens exhibit features distinctive of Fusioolithus, a type of fossil egg distinctive of the giant, long-necked titanosaurs.

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Finding non-avian dinosaur eggshells in high-latitude regions is relatively rare, as these areas likely provided difficult nesting challenges – such as low seasonal temperatures and extended periods of reduced sunlight. Discoveries in the Northern Hemisphere, particularly in Canada and Siberia, have been recorded but confirmed reports in the Southern Hemisphere are limited.

The titanosaurs were a group of four-legged herbivorous dinosaurs famous for their long necks and tails, as well as their small heads. The group included the largest land animals to have ever existed – with some even approaching the size of modern whales and tipping the scales at 70 tonnes.

The researchers found microscopic pores on the eggshells, which indicate that the eggs were completely buried in nest substrate (such as soil and organic matter) in a high-humidity environment during incubation. They note that the eggs were most likely incubated by the heat generated by the microbial decomposition of the substrate.

The Chorrillo Formation represents the highest paleolatitude (the latitude of a place at some point in the past) in the Southern Hemisphere where dinosaur eggshells have been definitively identified. Environmental reconstructions suggest that this region had a temperate-subtropical climate with high humidity and seasonal rainfall.

The discovery of the eggs represent the first direct evidence that titanosaurs were nesting at relatively high altitudes, suggesting they adapted their nest strategy to successfully reproduce, as prior eggshell discoveries indicate that they primarily nested in low- to mid-paleolatitudes.

Top image: Reconstruction of titanosaur nesting at a relatively high latitude in Argentina. Credit: Illustration: Masato Hattori