Researchers in northeastern Spain say they've uncovered hundreds of dinosaur egg fossils, including four kinds that had never been found before in the region. The eggs likely were left behind by sauropods millions of years ago.

Eggs, eggshell fragments and dozens of clutches were nestled in the stratigraphic layers of the Tremp geological formation at the site of Coll de Nargó in the Spanish province of Lleida, which was a marshy region during the Late Cretaceous Period, the researchers said.

"Eggshells, eggs and nests were found in abundance and they all belong to dinosaurs, sauropods in particular," the study's leader, Albert García Sellés from the Miquel Crusafont Catalan Palaeontology Institute, told Spanish news agency SINC this week.

"Up until now, only one type of dinosaur egg had been documented in the region: Megaloolithus siruguei," Sellés added. His team found evidence of at least four other species: Cairanoolithus roussetensis, Megaloolithus aureliensis, Megaloolithus siruguei and Megaloolithus baghensis. Megaloolithus eggs are thought to be associated with sauropods, long-necked dinosaurs that were among some of the largest to roam the planet.

The Coll de Nargó area is considered one of the most important dinosaur nesting areas in Europe, the researchers said, adding that their study shows it was used by several dinosaurs from the Late Campanian age (around 71 million years ago) to the Late Maastrichtian age (around 67 million years ago).

"We had never found so many nests in the one area before. In addition, the presence of various oospecies (eggs species) at the same level suggests that different types of dinosaurs shared the same nesting area," Sellés said, adding that the dinosaur eggs could help scientists determine the date of future findings at the site.

"It has come to light that the different types of eggs are located at very specific time intervals," Sellés explained to SINC. "This allows us to create biochronological scales with a precise dating capacity. In short, thanks to the collection of oospecies found in Coll de Nargó we have been able to determine the age of the site at between 71 and 67 million years."

The findings are published in the March issue of the journal Cretaceous Research.

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