Long-Necked Titanosaur Skeletons Have Surfaced at a Dinosaur Fossil Site in Transylvania
Transylvania may be known as the land of vampires, but it’s also home to a remarkable assortment of dinosaur fossils. About 70 million years ago, part of this region of Romania was separated from the mainland to form an offshore island where precipitation was abundant. The island’s swollen rivers would carry animal carcasses to an area today called the Hațeg Basin, where the remains of dinosaurs and other vertebrates are found today.
A new study published in PLOS One describes a particular site in the Hațeg Basin – called K2 – that is incredibly rich in vertebrate fossils, containing more than 800 in an area of less than five square meters (just over 50 square feet). K2 contains fossils belonging to fish, turtles, crocodiles, mammals and several dinosaurs.
Learn more: Why is the Isle of Wight rich in dinosaur fossils?
Diversity on a dinosaur island
The Hațeg Basin in Transylvania is world-famous for its dinosaur remains, discovered at dozens of sites over the past century. Despite the high number of fossil localities, dinosaur finds are generally considered rare in the region. One exception is the recently discovered site, where researchers found more than a hundred vertebrate fossils per square meter, with the large dinosaur bones almost on top of each other.
(Image credit: ELTE Eötvös Loránd University)
During the Late Cretaceous (around 100 to 66 million years ago), a diverse range of dinosaurs and other vertebrates inhabited Hațeg Island (now Hațeg Basin). The island today has a rather intriguing nickname: “the island of dwarf dinosaurs”.
The island received this name because many of the dinosaurs that lived there were much smaller than their mainland counterparts. Scientists have suggested that this is a prehistoric example of island dwarfism, an evolutionary process that causes larger animals on islands to shrink due to limited resources.
Insular dwarfism can be seen in some titanosaurs – a group of long-necked sauropods – that lived on Hațeg Island. For example, Magyarosaurus dacus was only about 20 feet long, while the mainland Patagotitan could reach 121 feet in length.
However, not all dinosaurs on Hațeg Island were this small. A February 2025 study in the Journal of Systematic Paleontology found that larger titanosaurs that migrated to the island via temporary land bridges lived alongside smaller species.
One of the largest pterosaurs, Hatzegopteryxalso lived on the island, with a wingspan of 33 to 39 feet. This is considered a case of island gigantism, in which smaller animals grow on islands due to reduced predation.
Washed away by floods
The dinosaurs that once roamed the island of Hațeg left behind remains that paleontologists have been digging up for years. But in 2019, researchers involved in the new study came across a particularly impressive hoard of bones preserved in layers of clay at the K2 site.
Dinosaur remains make up more than half (52%) of the fossil assemblage discovered at K2, with titanosaurs making up 62% of all dinosaur remains. After dinosaurs, turtle and crocodyliform fossils are the most common remains.
Researchers say K2 is so rich in fossils because of the subtropical climate that prevailed on Hațeg Island 72 million years ago. The island was populated by rivers that flowed from high areas into a basin, and during heavy rains, animal carcasses and living animals were washed away by high floodwaters that moved to lower areas.
“A detailed study of rocks from the K2 site indicates that a small lake once existed here, periodically fed by flash floods carrying animal carcasses. As river flow rapidly slowed upon entering the lake, the transported bodies accumulated in the deltaic environment along the shore, producing this exceptionally high bone concentration,” co-author Soma Budai, a researcher at the University of Pavia, said in a statement.
Connecting ancient ecosystems in Europe
Researchers discovered not only isolated bones at K2, but also partial dinosaur skeletons. Their findings provided insight into two different herbivorous dinosaurs; one is a 6.5 foot long, predominantly bipedal herbivore belonging to the Rhabdodontidae family, known for its stocky build and triangular skull, according to a newspaper article Fossil record. The other is a sauropod titanosaur dinosaur – researchers say there were no previously such well-preserved skeletons of this dinosaur in Transylvania.
According to the researchers’ findings, K2 now contains the oldest known vertebrate accumulation in the Hațeg Basin. That means the fossils will eventually help them compare K2 to younger fossil sites in Transylvania and learn more about the ecosystems occupied by dinosaurs in what is now Eastern Europe.
Learn more: 5 Massive Dinosaur Fossils and Where They Were Found
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