The journal Cretaceous Research is publishing an article which recognizes four different dinosaur eggs (oospecies) in the Coll de Nargó area (Lleida Province, south-central Pyrenees). The research proves the coexistence of different dinosaur species in this nesting area. The professors Xavier Delclòs, Ferran Colombo and Jaume Ortega, from the Department of Stratigraphy, Paleontology and Marine Geosciences of the UB, and some experts from the Catalan Institute of Paleontology (ICP) and the Spanish Geological and Mining Institute (IGME) participated in the research.
The Coll de Nargó area, located to the west of this town of Lleida Pyrenees, is considered to be one of the most important dinosaur nesting areas in Europe. It has yielded thousands of dinosaur eggs of Upper Cretaceous, eggshells and clutches attributed to sauropods which lived in this area about seventy millions years ago, little time before their extinction (65.5 million years ago). The research, whose main author is the expert Albert Garcia Sellés (ICP), who holds a PhD from the UB, also reports the first evidence of the oogenus Cairanoolithus outside of France. This discovery means a new connection between dinosaur species in France and the Iberian Peninsula in Upper Cretaceous. Up to now, only one specimen of dinosaur egg had been recognized in the Coll de Nargó area, Megaloolithus siruguei.
After having anlysed more than 30 levels across 370 m of Upper Cretaceous Tremp Formation deposits, the scientific research team identified four different oospecies: Cairanoolithus cf. roussetensis, Megaloolithus aureliensis, Megaloolithus siruguei and Megaloolithus cf. baghensis. Further, the co-occurrence of different ootaxa in the same level suggests that the nesting area was shared by different dinosaur taxa for a long time.
One of the main difficulties in Paleontology is to date accurately the fossils found. In the case of the different types of eggs, it is evident that they date from specific periods of time, so biochronological scales can be determined as a potential tool for dating. Thanks to the results of this research and its findings, it can be suggested that the age of Coll de Nargó rocks ranges from 71 to 67 million years ago.
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