Transylvanian Dinosaurs May Shed Light on Life in Europe 70 Million Years Ago

Earth’s landscapes have never been static—climate change and tectonic forces have continuously reshaped them over time. Even a few hundred thousand years ago, many regions looked vastly different from today: deserts once stretched where forests now stand, and ice sheets covered areas that are now warm. In this context, determining the environmental conditions in which dinosaurs lived 70 million years ago in what is now Transylvania may seem like a daunting challenge. However, geology provides researchers with powerful tools to uncover these ancient worlds.

Dr Gábor Botfalvai (pictured), the leader of the research team and a researcher at the HUN-REN Research Group for Palaeontology and the Department of Palaeontology at Eötvös Loránd University (ELTE), summarised the main objectives of the study: "We began excavations more than five years ago near the village of Valiora in Transylvania, where we uncovered hundreds of valuable dinosaur and other reptile remains across multiple sites. From the outset, our goal was not only to collect fossilised bones but also to determine the precise age and environment in which these animals lived."

To this end, the team carried out detailed geological mapping across a 10 km² area, analysed outcrops of various rock types, documented their fossil content, and collected key data to reconstruct the ancient ecosystem of the Hátszeg Basin. (Our previous report on research in the Hátszeg Basin is available here.)

The sedimentary rocks in the study area are not horizontal but steeply tilted, having been displaced from their original position by plate tectonic processes over millions of years. By studying the inclination of the strata and analysing the fractures that cut through them, researchers have been able to determine how the various dinosaur fossil sites discovered in the area relate to each other.

"Our geological mapping revealed that the fossil sites we studied span approximately 1.5 million years, allowing us to trace environmental and evolutionary changes over a longer timescale," said Dr Gáspár Albert, Associate Professor at the Institute of Cartography and Geoinformatics at Eötvös Loránd University (ELTE).

The grain size of the sedimentary rocks and the different structures observed within the layers provide valuable information for reconstructing the riverine environments that existed 70 million years ago. Using sedimentary geology methods, researchers can distinguish between different sub-environments within the riverine environment—determining where lakes and riverbeds were located, and whether the floodplain lay close to the river or several kilometres away.

The rocks studied not only contain bone remains but also thousands of microscopic fossils, such as tiny pollen grains, which are particularly useful for dating different terrestrial formations due to their distinct variations over time.

The findings show that the dinosaur fossil sites studied contain the remains of organisms that lived between 70 and 72 million years ago. "This makes our sites the oldest prehistoric vertebrate fossil sites in the Hátszeg Basin, providing valuable information about the composition of the region's ancient fauna and its subsequent evolution," summarises Dr Zoltán Csiki-Sava, a researcher at the University of Bucharest.

Photo credit: Dr Gábor Botfalvai