One of the dinosaur eggs found from the Jurassic treasure trove and (inset) principal investigator Muthuvairavasamy Ramkumar.

Geologists in Tamil Nadu have reported finding hundreds of fossilised dinosaur egg clusters dating back to around 65 million years buried in an ancient riverbed.

The eggs are around the size of a football (between 13 and 23 cm in diameter), team leader Muthuvairavasamy Ramkumar said.

"We are finalising a research communication with our German collaborators to be submitted for peer-review to an international publication. This is to scientifically document the find," he told Nature India.

Interestingly, the eggs were found in different layers buried underneath a stream in the Cauvery river basin, which means the dinosaurs perhaps inhabited the place year after year, he said. The eggs have volcanic ash deposits too suggesting that some sort of volcanic activity might have triggered their extinction.

The eggs were fossilised unhatched and also found to be infertile. "We need to study exactly what made them infertile," Ramkumar, head of the geology department in Periyar University said. Considering the presence of dense population of nests, it could be assumed that the dinosaurs might have lived in appreciable numbers, perhaps hundreds.

The eggs lay buried in a village in Ariyalur district near Tiruchirapalli. Earlier geologists have found fossils of marine alga, bivalves, gastropoda, telecypoda and brachiopoda in Ariyalur and neighbouring Perambalur district.

"The sedimentary rocks between Coleroorn and Vellar rivers north east of Ariyalur show the link between Deccan volcanism and environmental deterioration during the later part of Cretaceous era (140 to 65 million years). This is the period which witnessed the extinction of dinosaurs," Ramkumar said.

The site, teeming with hundreds of dinosaur eggs, must be preserved for future research, the geologists have urged.
The discovery of Sauropod and Carnosaur eggs was made on September 12, 2009 under an Indo-German project ECONDIA by Ramkumar and colleagues K. Anbarasu, T. Sugantha, G. Sathish and R. Suresh. Despite decades of study, the area remained largely unexplored. The geologists claim that this nesting site is perhaps the largest ever known in India, in terms of areal extent, presence of number of eggs, egg clusters, nesting pits and repetitive occurrence of these features at various stratigraphic levels.

The eggs were found heaped suggesting that the dinosaurs dug pits, laid eggs and covered them by loose sand just like crocodiles and turtles, the team surmises. "The dinosaurs might have squatted over a dug pit on sandy terrain and laid the eggs heaping them up," Ramkumar observes.

The team has also put forth a number of other hypothesis on extinction of Paleolithic life in the region and environmental stress causing infertility among the dinosaurs leading to their wipe-off. These need further investigation and corroboration.