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Paleontologists working in central India have made a rare discovery – a fossilized dinosaur hatchery with 92 nests and 256 eggs belonging to colonies of giant plant-eating titanosaurs.
A study of the nests and their bowling ball-sized eggs has revealed intimate details about the lives of the colossal, long-necked sauropods that roamed what is now central India more than 66 million years ago.
The eggs, which ranged between 15 centimeters and 17 centimeters (6 in and 6.7 in) in diameter, probably belonged to a number of titanosaur species. The number of eggs in each nest varies from one to 20, said study lead author Guntupalli Prasad, a paleontologist in the Department of Geology at Delhi University. Many of the nests were found close together.
The findings show that titanosaurs, among the largest dinosaurs that ever lived, weren’t always the most attentive parents, Prasad said.
“Because titanosaurs were of enormous size, the closely spaced nests would not have allowed them to visit the nests to maneuver and incubate the eggs or feed the hatchlings … as the parents would have stepped on the eggs and trampled them.”
Finding a very large number of dinosaur nests is unusual because the storage conditions must have been “just right” to have turned all the delicate eggs into fossils, said Dr. Darla Zelenicki, associate professor of dinosaur paleobiology at the University of Calgary in Canada, who studies dinosaur eggs. Zelenitsky was not involved in the research.
The first dinosaur eggs in the region were discovered in the 1990s, but the latest study focused on a nesting site in the Dhar district of Madhya Pradesh state, where excavations and fieldwork took place in 2017, 2018 and 2020.
The eggs found there were so well preserved that the team was able to detect degraded protein fragments from the eggshells.
The nesting behavior of titanosaurs shares characteristics with that of today’s birds and crocodiles, the study suggests.
From the proximity of the nests, the researchers concluded that the dinosaurs laid eggs together in colonies or nests, as many birds do today.
“Such nesting colonies would have been a sight to behold during the Cretaceous, when the landscape was dotted with a vast number of large dinosaur nests,” Zelenicki said.
Prasad said one particular egg — known as an egg-in-egg or egg-in-egg — that the team studied displayed avian reproductive behavior and showed that, like birds, some dinosaurs may have laid eggs sequentially. Ovum-in-ovo forms occur in birds when one egg implants into another egg that is still forming before they are laid.
“Sequential laying is the release of eggs one at a time with some time between two laying events. This is observed in birds. Modern reptiles, for example turtles and crocodiles, on the other hand, lay all the eggs together as a clutch,” he said.
The eggs would have been laid in marshy plains and buried in shallow pits, similar to the nesting sites of modern crocodiles, Prasad said. Like crocodile hatcheries, nesting near water may have been important to prevent eggs from drying out and offspring dying before hatching, Zelenicki added.
But unlike birds and crocodiles, which both incubate their eggs, Prasad said that, based on the physical characteristics of the nests, titanosaurs likely laid their eggs and then left the baby dinosaurs to fend for themselves — although more data is needed , to be sure.
Other dinosaurs were thought to be more attentive parents. A dinosaur was found in Mongolia in the 1920s, for example, lying near a nest with eggs believed to belong to a rival. Paleontologists at the time assumed the animal died while trying to rob the nest — and named the creature an oviraptor, or “egg thief.”
The reputation of the so-called dinosaur thief was not restored until the 1990s, when another discovery revealed that the eggs were actually his own, and that the creature had probably sat on them in a neatly arranged nest.
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