Hațeg Island was a large offshore island in the Tethys Sea during the Cretaceous period. It was situated in an area corresponding to the region around modern-day Hațeg, Romania.[1] Maastrichtian fossils of small-sized dinosaurs have been found in the erstwhile island's rocks.[2]
It was formed mainly by tectonic uplift during the early Alpine orogeny, caused by the Adriatic Plate's northwest movement across the Piemont-Liguria Ocean towards the end of the Cretaceous. There is no real present-day analog, but overall, the island of Hainan (off the coast of China) is perhaps closest as regards climate, geology and topography, though still not a particularly good match. The vegetation, for example, was of course entirely distinct from today, as was the fauna.
The Hungarian paleontologist Franz Nopcsa theorized that "limited resources" found on the island commonly have an effect of "reducing the size of animals" over the generations, producing a localized form of dwarfism. Nopcsa's theory of insular dwarfism — also known as the island rule — is today widely accepted.
About nine species of dinosaurs, and one species of pterosaur are thought to have been indigenous to the island. Most of these animals were smaller versions of mainland megafauna, which became smaller due to island dwarfism, although this is certainly not the case for Hatzegopteryx which, being one of the biggest pterosaurs ever, is an example of island gigantism. Among them are included: