Scientists find over 92 clutches of giant dinosaurs in India

Scientists have identified at least 92 nests containing dinosaur eggs at a paleontological site near Dhar district in Madhya Pradesh state, India.

Between fragments and preserved whole eggs, the clutches contained 256 eggs, thus representing one of the largest dinosaur “nursery” areas in the world.

The age of the rocks where the fossil eggs were found is from the end of the Cretaceous, between 72 and 66 million years old, and they were covered by calcareous sediments.

The eggs are possibly from titanosaurs, a group of long-necked dinosaurs that lived between 145 and 66 million years ago and could reach 40 meters in length.

It is likely that at least six different dinosaur species used the site for nesting.

The findings were published in this Wednesday’s edition (18) of the specialized magazine PLoS One. The study was part of Harsha Dhiman’s doctoral research developed at the Geology department of the University of New Delhi and coordinated by researcher Guntupalli Prasad.

So far, paleontologists have not found bone remains of the animals, including fossilized embryos, that could help identify the species of dinosaurs that made their nests in the region.

Fieldwork in the region began many years ago, when an amateur paleontologist found the first dinosaur eggs from the Lameta formation, where the fossiliferous site is located. Dhiman’s research in the region, which began in 2017, found plenty of new materials.

“We were already aware of some litters, but there were two cities that had not yet been explored, and so we decided to go through them in December 2017, where we did fieldwork for a month. In three consecutive trips to the collection site, we found dozens of new nests with preserved eggs”, says the paleontologist.

The job of removing the eggs took three years to complete. In the laboratory, microscopic analyzes of the structure that formed the eggshells and even of the sediment found inside allowed for some interesting discoveries.

For example, the researchers recorded eggs with multiple shells, which is characterized by the same egg receiving the outer layer that makes up the shell more than once in the reproductive system, making the egg unviable. The phenomenon is known as “ovum-in-ovo” (ovum-in-ovo), when, before being deposited in the ground, the egg returns to the previous stage and is embedded in another egg still in formation.

Such pathologies are common in birds, possibly indicating similarities of the reproductive system of titanosaurs with these previously unknown animals. “Theropod dinosaurs and birds, which have a common origin, possibly had this same type of condition occurring at the time of egg formation, but it is rare to find it in titanosaurs, a group far from birds”, explains the researcher.

As these processes make the embryo unfeasible, many of the litters were found with unhatched eggs. In addition to these, other eggs placed near areas subject to flooding and exposed to the weather also failed to hatch, possibly indicating that titanosaurs buried their eggs, as current crocodiles do.

No adult individuals associated with eggs were found. “If the animals were there, it is likely that their preservation also occurred, suggesting that the titanosaurs used that place as a nursery, but they went in search of food in another region, as crocodiles do”, he says.

The researchers have identified at least three types of egg disposition that help to elucidate the biology of the animals. “We know that this type of disposition indicates a sequential way of laying the eggs and is similar to what we see in birds, in which colonies are formed to lay the eggs in the same place”, explains Prasad.

“We removed some eggs to do more in-depth analyses, including computed tomography in search of bone elements that would indicate which animals they belonged to, but, as they have a very high density, the X-ray machines we have at the university were not able to take the radiograph. “, laments.

The similarities of the site in India with other sites already known with dinosaur eggs, such as Argentina and Spain, however, allow comparing the structure of the fossils with others and thus knowing a little more about the uniqueness of this find.

“Added to the two other sites in India that had already been explored, we have an extension of more than 900 kilometers from east to west of a dino nursery from the late Cretaceous, making the Lameta formation site one of the largest and most important in the world. “, he adds, saying that he awaits collaborations and new resources for research that may allow future studies to investigate the animals that lived there.