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For several years Chiappe and his colleagues have been unearthing thousands of fossils from a site called Loma del Pterodaustro in central Argentina. Every fossil, with the exception of a few fish fossils, has been identified as a Pterodaustro pterosaur.
"It gets to the point where we have such a large sample, you have to wonder. How could it be that all we find here are Pterodaustro? I would say it has something to do with the environment," Chiappe said.
He concludes that the site was unsuitable to all but this flamingo-like pterosaur. The area was perhaps filled with extremely salty lakes similar to those inhabited by flamingoes high in the Andes mountains, Chiappe speculated. Pterodaustro was a filter feeder, just like the flamingo, he added. Filter feeders get food by filtering it from water.
Chiappe and his colleagues found the fossilized Pterodaustro embryo among hundreds of other fossils, ranging from young juveniles to full-grown adults. This suggests that the reptiles nested in a colony and protected their young, he said.
"They didn't lay their eggs and leave off for somewhere else like most reptiles do—lay their eggs and say, That's it, hasta la vista," he said. "In reality they guarded the nests and presumably guarded the hatchlings."
Bennett said interpretation of the site as a large Pterodaustro colony makes sense, noting that many seabirds do the same today. "In seabirds we see large colonies. It's reasonable to suppose the same with some pterosaurs as well," he said. "But there's no reason to think they all did."
The Chinese team reports in Nature that their new fossil resembles the pterosaur known as Beipiaopterus and is "longer and narrower" than the pterosaur reported from China in June. The new fossil was found in the Yixian formation, which has become famous for dinosaur discoveries in recent years.
Both Chinese pterosaur fossil embryos are of similar age and were found in similar environments. According to Bennett, this suggests that a number of different pterosaurs may have nested around this ancient lake-filled Chinese environment.
Luis Chiappe's research is funded in part by a grant from the National Geographic Society's Committee for Research and Exploration.
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