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Treasure trove of fossil eggs hints titanosaurs nested in colonies

A treasure trove of fossil nests uncovered in India hints at an array of as-yet-undiscovered dinosaurs belonging to the titanosaur group, and gives clues to how these animals reproduced.

A total of 92 nests and 256 eggs, measuring up to 20 centimetres long, were found in the Lameta Formation, a sequence of rock layers well-known for containing fossils of immense, long-necked dinosaurs called titanosaurs. Palaeontologists had previously identified three titanosaur species from bones found in this area.

Guntupalli Prasad at the University of Delhi and his colleagues discovered the nests during fieldwork between 2017 and 2020. The team proposes that there are at least six egg shapes – technically called oospecies – found in the formation. If each egg shape was laid by a different species, it would double the known number of species in the formation.

The nests also underscore what palaeontologists are coming to understand about how some of the largest dinosaurs reproduced. The nests were made up of egg clutches laid in shallow pits, much like those of modern crocodiles. And while the number of nests found close together indicate that these dinosaurs gathered to lay eggs, just like many modern birds, the nests are so close to each other that there was no room for the adults to stick around. This suggests these dinosaurs employed a “lay ‘em and leave ‘em” strategy like that of some sea turtles, where the next generation was left to hatch and wander out onto the landscape on their own.

Darla Zelenitsky at the University of Calgary in Canada, who wasn’t involved with the study, urges caution on taking the six different egg types as a sign of six different species. Larger or smaller individuals of the same species might lay eggs that superficially seem different, or different species might lay eggs that are indistinguishable, she says.

Finding bones and eggs together will provide firmer evidence of how many dinosaur species were around, says Zelenitsky. “That said, there is clearly something interesting about the Lameta Formation to consistently produce a number of different titanosaur egg types,” she says.

Read more:

Fossilised nest shows some dinosaurs sat on their eggs like birds do

Back in the heyday of the dinosaurs, this part of western India was a wet and marshy lowland dotted with small lakes. “The flats offered sites close to water sources, soft soil for nest burial and possible availability of food for juveniles,” says Prasad, all of which would have made the area attractive to these dinosaurs.

These moist sediments also help explain why so many dinosaur nests came to be preserved in western India. When streams, marshes and ponds rose, nearby nests were inundated and buried.

PLoS One DOI: 10.1371/journal.pone.0278242

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