(CNN) A previously unknown dinosaur with a remarkably flat head lived around 70 million years ago on an island home to dwarfed prehistoric creatures.
Discovered in what's now western Romania, the Transylvanosaurus platycephalus (flatheaded reptile from Transylvania) was 2 meters (6 feet) long — a relatively small size for a dinosaur, according to a new study. Its skull bones were unearthed in 2007 in a riverbed of the Haţeg Basin.
In the Cretaceous Period, this region of Romania was a tropical archipelago. Dinosaurs living there were smaller than their relatives elsewhere; paleontologists think these dinosaurs were an example of what biologists call "island rule," where large animals isolated on islands become dwarfed or stunted in their growth over time and small animals become larger.
Sauropods, the largest type of dinosaurs that have ever lived, reached average heights of a puny 6 meters (nearly 20 feet) on the archipelago, for example, compared with 15 to 20 meters (49.2 to 65.6 feet) typical for the group.
However, the mechanism that gives rise to such changes isn't fully understood but could be linked to a shortage of resources.
The dinosaur's bones were able to survive for tens of millions of years because the sediments of an ancient riverbed protected them.
"If the dinosaur had died and simply lain on the ground instead of being partly buried, weather and scavengers would soon have destroyed all of its bones and we would never have learned about it," study coauthor Felix Augustin, a paleontologist and doctoral student at the University of Tübingen in Germany, said in a news release.
None of the bones the researchers uncovered was longer than 12 centimeters (about 5 inches), but they revealed a remarkable amount of detail about the little plant-eating dino that would have walked on two legs and had a powerful, thick tail. It was possible to discern the contours of the brain of Transylvanosaurus, the research team said.
"We were able to see the impressions, and thus the proportions, of different brain sections — more specifically, of the olfactory bulbs (the brain section responsible for the sense of smell) and the cerebrum, which serves several different functions from sensory processing to memory," Augustin said via email.
"The next step would be to compare the proportions of the brain and eye to other related species, as this may give information on what senses were important to Transylvanosaurus," he added.
The Haţeg Basin has been a hotbed for dinosaur discoveries. Ten dinosaur species have already been identified during excavations in the region, with the first dinosaur discovered in 1900. The Transylvanosaurus platycephalus is the first new dinosaur species to be discovered there in 10 years after a small carnivore and long-necked plant eater were found in 2010, Augustin said.
Transylvanosaurus was a plant eater and part of a family of dinosaurs known as Rhabdodontidae that were common during the Late Cretaceous Period. Its head was far wider than other Rhabdodontidae species, the study said.
Precisely how the Transylvanosaurus ended up in the eastern part of what was the European archipelago remains unclear.
Researchers believe this type of dinosaur could have originated in what's now France, where fossils of its nearest relatives have been found, and somehow made it to the region — perhaps by swimming, or due to fluctuations in sea level or tectonic processes that created a land bridge.
"They had powerful legs and a powerful tail," Augustin said of the Transylvanosaurus. "Most species, in particular reptiles, can swim from birth."
Another possibility is that various lines of rhabdodontid species evolved in parallel in Eastern and Western Europe.
Regardless of its geographic origins, the newly discovered species helps disprove assumptions that there was a low diversity of dinosaurs and other fauna in the Late Creaceous Period, the researchers said. As well as the dwarf dinosaurs, the Haţeg Basin was also home to crocodiles, giant pterosaurs (flying reptiles) and turtles — before dinosaurs went extinct 66 milion years ago.
"Almost every terrestrial animal on this island was pretty small," Augustin said via email. "An exception were the pterosaurs, some of which reached gigantic body sizes — the reason for this is probably that they could fly and thus were not as severely impacted by the limited resources on the island."
The research was published November 23 in the Journal of Vertebrate Paleontology.