The creatures lived on an island – a kind of pigmy Jurassic Park – and were up to eight times smaller than some of their mainland cousins.
One of the island-dwelling dinosaurs, named Magyarosaurus, was little bigger than a horse, but was related to some of the largest creatures to ever walk the Earth – gigantic titanosaurs such as Argentinosaurus, which reached up to 100 feet long and weighed around 80 tons.
Another of the dinosaurs was found to be a primitive dwarfed species similar to large duck-billed herbivores like Iguanodon, which could grow to be up to 10 feet long and weighed more than three tons.
Fossils from the dwarf dinosaurs were found in what is now modern day Romania, in an area known as Hateg, which, 65 million years ago – when the creatures were living there – was an island.
Professor Michael Benton, from the University of Bristol, who carried out the research with scientists at the Universities of Bucharest and Bonn, said the dinosaurs seemed to have evolved smaller bodies after becoming marooned there.