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Rare egg fossils reveal dinosaurs weren't doting parents

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Paleontologists working at the center India has made a rare discovery – a fossilized dinosaur hatchery with 92 nests and 256 eggs belonging to colonies of giant herbivorous titanosaurs.

A study of the nests and their bowling ball-sized eggs has revealed intimate details about the life of the colossal long-necked species. sauropods that crossed what is now central India more than 66 million years ago.

The eggs, which ranged between 15 centimeters and 17 centimeters (6 inches and 6.7 inches) in diameter, likely belonged to several species of titanosaurs. The number of eggs in each nest ranged from one to 20, said study lead author Guntupalli Prasad, a paleontologist in the geology department at the University of Delhi. Many of the nests were found close to each other.

The findings suggest that titanosaurs, among the largest dinosaurs that ever lived, weren’t always the most attentive parents, Prasad said.

“As titanosaurs were huge in size, close nests would not allow them to visit to maneuver and incubate the eggs or feed the young…

Dinosaur eggs are fragile, making their survival in the fossil record very rare.

Finding such a large number of dinosaur nests is unusual, as preservation conditions need to be “exact” to turn all the delicate eggs into fossils, said Dr. Darla Zelenitsky, an associate professor of dinosaur paleobiology at the University of Calgary in Canada, who studies dinosaur eggs. Zelenitsky was not involved in the research.

The nests were close together, suggesting that dinosaurs laid eggs in groups, similar to many modern-day birds that form colonies.

The first dinosaur eggs in the region were discovered in the 1990s, but the most recent study focused on a nesting site in the Dhar district. in the state of Madhya Pradesh, where excavations and fieldwork took place in 2017, 2018 and 2020.

The discovered eggs were so well preserved that the team was able to detect fragments of degraded proteins in the eggshells.

The nesting behaviors of titanosaurs shared traits with today’s birds and crocodiles, the research suggested.

From the proximity of the nests, the researchers inferred that dinosaurs laid eggs together in colonies or aviaries, as many birds do today.

“Such nesting colonies would have been a sight to behold in the Cretaceous, where the landscape would have been dotted with large numbers of large dinosaur nests,” Zelenitsky said.

Prasad said that one egg in particular – known as an ovo-in-ovo, or ovo-in-ovo – that the team studied showed bird-like reproductive behavior and indicated that, similar to birds, some dinosaurs may have laid eggs. sequentially. egg-in-egg forms occur in birds when an egg is embedded in another egg still in the process of formation before being laid.

“Sequential laying is the release of eggs one by one with some time interval between two laying events. This is seen in birds. Modern reptiles, for example turtles and crocodiles, on the other hand, lay all their 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. Similar to crocodile hatcheries, nesting close to water may have been important in preventing the eggs from drying out and the young dying before hatching, Zelenitsky added.

Titanosaur eggs measured 6 to 7 inches in diameter.

But unlike birds and crocodiles, which 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 have assurance.

Other dinosaurs were considered more attentive parents. A dinosaur was discovered in Mongolia in the 1920s, for example, near a nest of eggs thought to belong to a rival. Paleontologists at the time assumed the animal had died trying to loot 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, in fact, their own and that the creature was probably sitting on them in a neatly arranged nest.