Dinosaur bones found almost on top of each other in Transylvania
Scientists exploring Romania’s Hațeg Basin have discovered one of the densest dinosaur fossil sites ever found, with bones lying almost on top of each other. The K2 site preserves thousands of remains from a prehistoric flood-fed lake that acted like a natural bone trap 72 million years ago. Alongside common local dinosaurs, researchers uncovered the first well-preserved titanosaur skeletons ever found in the region. The site reveals how ancient European dinosaur ecosystems formed and evolved in the final chapter of the age of dinosaurs.
The Hațeg Basin in Transylvania has long been known around the world for its dinosaur fossils, uncovered at dozens of sites over the last hundred years. Even so, complete dinosaur discoveries are usually uncommon across the region. That pattern changed with the identification of a newly studied site where scientists documented more than 100 vertebrate fossils per square meter, including large dinosaur bones lying almost directly on top of one another.
Years of Fieldwork Lead to an Exceptional Fossil Find
For more than five years, the Valiora Dinosaur Research Group, made up of Hungarian and Romanian paleontologists, has been carrying out fieldwork in the western Hațeg Basin. The rocks examined there date back to the Upper Cretaceous and capture the final few million years before dinosaurs disappeared. Excavations have revealed fossil-rich deposits containing thousands of remains from amphibians, turtles, crocodiles, dinosaurs, pterosaurs, and mammals.
Among all the sites explored, one location known as K2 stands out. From an area measuring less than five square meters, researchers recovered more than 800 vertebrate fossils, making it the richest site documented so far. The full scientific analysis of this discovery was recently published in the journal PLOS ONE.
A Defining Moment in the Field
"In 2019, during our first field survey in the Hațeg Basin, we almost immediately came across the K2 site. It was a defining moment for us -- we instantly noticed dozens of large, exceptionally well-preserved black dinosaur bones gleaming in the grey clay layers exposed in the streambed. We immediately began our work, and through several years of excavation we collected an extraordinarily rich vertebrate assemblage from the site," explained Gábor Botfalvai, assistant professor at the Department of Paleontology, Eötvös Loránd University, and leader of the research group.
How Ancient Floods Created a Bone-Rich Landscape
About 72 million years ago, the region that is now the Hațeg Basin experienced a warm, subtropical climate shaped by temporary river systems. These rivers flowed from higher terrain toward the basin and frequently spilled over their banks during heavy rainfall. As floodwaters surged downstream, they gathered animal carcasses from the surface, along with living creatures and skeletal remains caught in their path.
"Detailed study of the rocks at the K2 site indicates that a small lake once existed here, which was periodically fed by flash floods carrying animal carcasses. As the flow of the rivers slowed rapidly upon entering the lake, the transported bodies accumulated in the deltaic environment along the shore, producing this exceptionally high bone concentration," said Soma Budai, researcher at the University of Pavia and co-author of the publication.
Rare Dinosaur Skeletons Reveal New Scientific Insights