Dinosaur eggs

In News: A group of Indian researchers found rare cases of fossilised dinosaur eggs — an egg within an egg — among 256 newly discovered eggs from the Narmada Valley.

• 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.

Unique discovery:

• The unique feature of egg within the egg has not been reported from any other dinosaur or even in other reptiles.
• Help to understand the diet and the type of water consumed and the environment in which the eggs were deposited.
• Fossilised eggs provide clues on reproductive biology, nesting behaviour and parental care

About the discovery:

• Titanosaurs — one of the largest dinosaurs to have roamed the Earth — displayed a notable reproductive trait unique to modern-day birds.
• The egg has two yolks; this feature can be seen in birds, suggesting they share similar reproductive traits.
• They nested in colonies, a feature found in about 13 per cent of modern-day birds. They also laid eggs in sequential order like avian species.
• Titanosaurs buried their eggs in shallow pits, a behaviour seen in modern-day crocodiles.
• The eggs belonged to six species, suggesting a higher diversity of these extinct giants in India.
• 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 hatchings were forced to fend for themselves
• Dhiman speculates that 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, she added.
• 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

Location:

• 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.

Previous Year Question

Q1) The word ‘Denisovan’ is sometimes mentioned in media in reference to (2017)

1. fossils of a kind of dinosaurs
2. an early human species
3. a cave system found in North-East India
4. a geological period in the history of Indian subcontinent

Source: DTE