Paleontologists in Switzerland have unearthed what may turn out to be Europe's largest dinosaur mass grave.

About 300 dinosaur bones were found in Frick, a Swiss village near the border with Germany, said Monica Rumbeli, director of the village's dinosaur museum.

The skeletons of two Plateosaurus dinosaurs were first spotted by an amateur paleontologist, 10 metres apart, at a construction site for a house.

Martin Sander, a paleontologist at the University of Bonn, told Reuters the area could extend for 1.5 kilometres, which would make it the biggest excavation site for dinosaur bones in Europe.

It's possible more animals in the herd became stuck in marshland that scientists believe was part of a river delta.

Scientists say the Plateosaurus, believed to be plant-eater, roamed Europe more than 200 million years ago during the late Triassic period.

The Plateosaurus measured six to eight metres long. It had a small skull and long neck and each forelimb had a large pointed thumb claw, probably for feeding and defending itself.