Fossilised dinosaur eggs found in Narmada valley

Key findings-

• The discovery suggests that Titanosaurs — one of the largest dinosaurs to have roamed the Earth — displayed a notable reproductive trait unique to modern-day birds. 
• The unique feature of egg within the egg has not been reported from any other dinosaur or even in other reptiles,
• The egg has two yolks; this feature can be seen in birds, suggesting they share similar reproductive traits.
• The team discovered 92 nesting sites containing 265 fossilised eggs  measuring 15-17 centimetres in diameter  during field investigations in the Dhar district of Madhya Pradesh between 2017 and 2020.
• The fossils were from the Late Cretaceous period.
• This region falls between the easternmost Lameta exposures at Jabalpur in the upper Narmada Valley (central India) and Balasinor in the west in the lower Narmada Valley (western central India).

• Lameta exposure is a sedimentary rock formation known for its dinosaur fossils. These sedimentary rocks are mostly exposed along the Narmada Valley. 
• The fossil records here are largely concealed by Deccan volcanic flows, which prevents their removal by erosion.
• The eggs belonged to six species, suggesting a higher diversity of these extinct giants in India. Further, Titanosaurs buried their eggs in shallow pits, a behaviour seen in modern-day crocodiles.
• They nested in colonies, a feature found in about 13 percent of modern-day birds. They also laid eggs in sequential order like avian species.
• Parental care was likely absent as the eggs were laid too close to each other. The spacing did not provide room for adults, suggesting that hatchlings were forced to fend for themselves.
• However, the egg-in-egg feature did not benefit the dinosaurs. The pore canals get blocked due to the presence of two eggshell layers, one above the other. This could asphyxiate the embryo.
• Among the fossils, the team also found unhatched eggs. Infertility, embryo death before hatching and deep burial could have contributed to their death. Environmental factors such as floods could also be involved.
• Fossilised eggs provide clues on reproductive biology, nesting behaviour and parental care.
• Moreover, stable isotope studies of eggshells can help us understand the diet and the type of water consumed and the environment in which the eggs were deposited.