A study of European dinosaurs has revealed something very different from what was happening across the Atlantic at the time. The study supports the theory that the drastic loss of species at the end of the Cretaceous was a result of a single asteroid strike, rather than a combination of factors.
Although the idea of death from above has grabbed popular imagination, many paleontologists believe that the story is more complex. While the asteroid definitely seems to have delivered the coup de grâce, species were disappearing for millions of years beforehand, leading to a search for more gradual influences, such as volcanic activity from the Deccan Traps.
It might be expected that this debate would be based on worldwide evidence, but in fact most studies from the last part of the Cretaceous come from North America. The geology of western Canada and the United states at the time produced a rich store of fossils, and the locations are easily accessible to the major paleontological research institutes.
However, both the French and Spanish sides of the Pyrenees also have latest Cretaceous specimens. By combining the findings from this region with those from Romania and less abundant sites, a team from five European nations has concluded that the same pre-asteroid decline was not seen on that continent. The work has been published in Zookeys.
"For a long time, Europe was overshadowed by other continents when the understanding of the nature, composition and evolution of latest Cretaceous continental ecosystems was concerned. The last 25 years witnessed a huge effort across all Europe to improve our knowledge, and now we are on the brink of fathoming the significance of these new discoveries, and of the strange and new story they tell about life at the end of the Dinosaur Era," said lead author Dr. Zoltán Csiki-Sava of the University of Bucharest.
“Although Europe had experienced some ecological reorganization during the waning years of the Cretaceous, there is no strong evidence that dinosaurs and other organisms gradually wasted away to extinction,” the authors conclude.
The paper also reveals an interesting picture of the way European animals, including dinosaurs, mammals, turtles and crocodilians, diverged from those elsewhere. Europe was lower lying at this time, before collision with Africa raised parts of the continent, and the high sea levels of the era turned it into an archipelago of islands. Isolation led to rapid diversification as species adapted to local circumstances, although exchange continued with Gondwanaland, and between islands during periods where sea levels declined.
One of the effects the authors observe are cases of island dwarfism among dinosaurs, such as Magyarosaurus, a Titanosaur that doesn't live up to the name, being a modest six meters long.
Credit: Verónica Díez Díaz/Csiki-Sava et al. Vertebrae from late Cretaceous European Titanosaurs, with Magyarosaurus at D.
The same fossil deposits are also revealing a pattern of extinction and survival among mammal, reptile and amphibian species across the Cretaceous/Paleogene boundary, while local bird species seem to have died out entirely.