Researchers discovered hundreds of dinosaur egg fossils in the Coll de Nargó area of northwestern Spain, including the eggs of four dinosaurs previously unknown to the reigon, which researchers are considering a paleontological breakthrough. 

The eggs are believed to have come from sauropods, quadruped dinosaurs with long necks and tails. The brachiosaurus might be one of the best-known sauropods.

"Eggshells, eggs and nests were found in abundance and they all belong to dinosaurs, sauropods in particular. Up until now, only one type of dinosaur egg had been documented in the region: Megaloolithus siruguei. After analyzing more than 25 stratus throughout the Tremp Formation, a minimum of four different additional types were identified: Cairanoolithus roussetensisMegaloolithus aureliensisMegaloolithus siruguei and Megaloolithus baghensis," said Albert García Sellé, the lead scientist in the study.

The findings drew ties between dinosaurs that roamed the lands of what are now knows as France and Spain. The discovery of the Cairanoolithus fossils are significant because previously eggs of the Cairanoolithus were only known in the south of France. The newly found egg fossils are the first of their kind to be found on the Iberian Peninsula.

The dig site at Coll de Nargó is eight kilometers west of Lleida, a town close to the French border.

The findings support theories which suggest that sauropods used Coll de Nargó as a nesting reigion for millions of years.

"It has come to light that the different types of eggs (oospecies) are located at very specific time intervals. 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," García Sellé said.

Sites like Coll de Nargó are considered to have significant scientific value because they allow scientists to understand and reconstruct ecosystems at the end of the Mesozoic Era.