A team including UCL researchers has identified two new dinosaur species found in present-day Romania that lived shortly before dinosaurs went extinct.
The end of the Cretaceous Period, 66 million years ago, marked the dramatic extinction of the dinosaurs following an asteroid impact. Until now, our understanding of this mass extinction has been largely shaped by fossils from North America.
But a new study, led by Dr Verónica Díez Díaz from the Museum für Naturkunde Berlin, has highlighted the crucial role of European fossil discoveries in providing a more comprehensive picture of this extinction episode.
The researchers reported on two new sauropod species, Petrustitan hungaricus and Uriash kadici, found in the fossil-rich Hațeg Basin in western Romania. In the Cretaceous Period, this area was a large island roughly the size of Ireland.
Their findings, published in the Journal of Systematic Palaeontology, revealed that the diversity of these long-necked plant-eating dinosaurs in Europe during the Late Cretaceous was far greater than previously thought.
Fifteen years ago, only five sauropod species were known from this time period. As of now, at least 11 have been identified - a contrast to North America, where only one sauropod species from the same epoch has been documented.
The study has also shown the connections between European dinosaurs and their relatives in Africa, Asia, and South America.
Co-author Professor Paul Upchurch (UCL Earth Sciences) said: "Migrations facilitated by temporary land bridges or even swimming across seas more than 500 kilometres may have contributed to this diversity."
Co-author Professor Philip Mannion (also UCL Earth Sciences) added: "Some of these dinosaurs were descendants of earlier faunas, while others arrived in the region only recently."
Lead author Dr Díez Díaz said: "The extraordinary diversity in a small geographic area like Hațeg Island is remarkable. Here, sauropods of various sizes co-existed: from giants more than 10 metres long and weighing 8 tonnes to dwarfs just 2.5 metres in length and less than 1 tonne in weight. This provides fascinating insights into the environmental conditions that allowed the co-existence of different species."
Traditionally, it was believed that the dinosaurs of what was at that time Hațeg Island adapted to their limited habitat by becoming smaller - a phenomenon known as "island dwarfism". However, the discovery of the large sauropod Uriash challenges this assumption. Dr Zoltán Csiki-Sava from the University of Bucharest said: "Local evolution was more complex than previously thought, showing that not all species reduced their size."
Although this research has expanded our understanding of European titanosaurs, much remains to be discovered. Dr Díez Díaz said: "New fossil sites continually provide fresh material that helps us better understand the past." The team is confident that Europe's fossil discoveries will continue to change our understanding of the Cretaceous Period.
