Picture this: You're a dinosaur living in the Cretaceous period. You are looking for good nesting sites that will keep your eggs safe and warm. Where do you go?
A paper in Nature Communications today reports that some dinosaurs regularly returned to geothermal areas to nest. The new discovery of a nesting site in Sanagasta Valley in La Rioja province, northwestern Argentina show that some neosauropods used the area to keep their eggs warm. Eighty clutches of eggs were mapped to be within 3 meters of geothermal conduits which would keep the eggs at 60–100°C for the incubations period of 1-2 months. Most of the nests contained 3 to 12 eggs but some had as many as 35, stacked in 2 tiers. The nests themselved could be as large as 2 square meters. The large number of eggs suggests that these dinosaurs were boosting their young's chances of survival -- the more you lay the more likely that more will survive.
An analysis of the elements in the eggshells and associated sediments showed that the eggs were present in the area during the Gondwanic hydrothermic cycle. This period of geothermal venting is known to have occurred between 134 to 110 million years ago. The egg shells were found to be thick and the whole eggs large, about 21 cm in diameter. The size of the eggs and the thickness of the shells is thought to have protected the eggs from the steamy, acidic enviroment found around the vents. Because the shell thickness ranged from 1.29 to 7.54 millimeters, it is suggested that the shells got thinner over the incubation period, likely due to the acidic moisture.
As of yet, no fossilized bones have been found at this site. Scientists are still looking for fossils in order to pin down the species.
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