Fossil egg find hints that titanosaurs nested in colonies

A study of more than 250 fossil eggs found in India suggests that long-necked titanosaurs nested in large groups, but left the hatchlings to fend for themselves.

A treasure trove of fossil nests found in India hint at the many yet undiscovered dinosaurs belonging to the titanosaur group and provide clues to how these animals reproduced.

A total of 92 nests and 256 eggs up to 20 centimeters long have been found in the Lamet Formation, a sequence of rock layers well known for containing the fossils of huge, long-necked dinosaurs called titanosaurs. Paleontologists have previously identified three species of titanosaurs from bones found in the area.

Guntupalli Prasad of the University of Delhi and colleagues discovered the nests during field work between 2017 and 2020. The team suggests that at least six egg-shaped forms, technically called oovids, were found in the formation. If each egg form were laid by a different species, this would double the known number of species in the formation.

The nests also highlight what paleontologists are beginning to understand about how some of the largest dinosaurs bred. Nests were made from egg clutches laid in shallow pits, similar to modern crocodiles. And while the number of nests found close together indicates that these dinosaurs gathered to lay their eggs, like many modern birds, the nests are so close together that the adults had no room to stay close. This suggests that these dinosaurs used a “put ’em and leave” strategy, like some sea turtles, with the next generation hatching and roaming the landscape on their own.

Darla Zelenitsky of the University of Calgary in Canada, who was not involved in the study, cautions that six different egg types should be treated with caution as a sign of six different species. Larger or smaller individuals of the same species may lay eggs that appear different at first glance, or different species may lay eggs that are indistinguishable from each other, she says.

Finding bones and eggs together will provide stronger evidence of how many species of dinosaurs existed around, Zelenitsky said. “However, there is clearly something interesting about the Lamet Formation as it constantly produces several different types of titanosaur eggs,” she says.

Even during the heyday of the dinosaurs, this part of western India was a wet and swampy lowland dotted with small lakes. “The flats offered sites close to water sources, soft soil for nest burials, and possible food availability for the young,” Prasad says, all of which made the area attractive to these dinosaurs.

These wet deposits also help explain why so many dinosaur nests survive in western India. When streams, swamps and ponds rose, nearby nests were flooded and buried.