Dwarf dinosaur fossils have been found in Hateg, Romania. During the Late Cretaceous period, much of the land area of eastern Europe was inundated by the waters of the Tethys Sea. Thus, the land existed in the form of islands.

Dinosaurs, along with other animals and plants, were isolated on these islands, cutting the flora and fauna off from other larger landmasses. Over time, the dinosaurs on these islands became smaller in response to the limited ecological environment. For example, the Telmatosaurus, a primitive hadrosaur found in Hateg, was about 15 feet (5 meters) long, and weighed approximately 1,10 pounds, or just over a half ton (450 kilograms). This is about one-third the length and one-tenth the weight of other Telmatosaurus fossils found in other parts of the world. The larger dinosaurs were able to take advantage of greater territories and habitats, growing much more than their smaller, island-bound cousins.