21st January, 2023 Geography
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- Indian researchers found rare cases of fossilized eggs — an egg within an egg — among 256 newly discovered eggs from the Narmada Valley.
- 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.
- Titanosaurs were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thriving at the time of the extinction event at the end of the Cretaceous.
- Titanosauria have the largest range of body size of any sauropod clade.
- One of the largest titanosaurs, Patagotitan, had a body mass estimated to be 69 tonnes , whereas one of the smallest, Magyarosaurus, had a body mass of approximately 900 kilograms.
- Researchers found rare cases of fossilized eggs — an egg within an egg — among Titanosaurs.
- The unique feature of the 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 eggs belonged to six species, suggesting a higher diversity of these extinct giants in India. Further, Titanosaurs buried their eggs in shallow pits, a behavior 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 hatchings were forced to fend for themselves.
- 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.
Area of Discovery:
- 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.
- This region falls between the easternmost Lameta exposures at Jabalpur in the upper Narmada Valley and Balasinor in the west in the lower Narmada Valley.
- 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.
Significance of recent Findings:
- 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.