Scientists in south-western France have uncovered a giant dinosaur thigh bone at an excavation site that has been yielding fossils for nearly a decade, the BBC reports.

Two metres (6.6ft) long, the femur found at Angeac is thought to have belonged to a sauropod, a plant-eating dinosaur with a long neck and tail.

Sauropods, common in the late Jurassic era, were among the largest land animals that ever existed.

Palaeontologists say they are amazed at the state of preservation of the bone.

"We can see the insertions of muscles and tendons, and scars," Ronan Allain of the National History Museum of Paris told Le Parisien newspaper.

"This is rare for big pieces which tend to collapse in on themselves and fragment."

Such dinosaurs, which lived more than 140m years ago, would have weighed 40 to 50 tonnes, Allain told Reuters news agency.

A sauropod thigh bone found at the same site in 2010 was 2.2m long and weighed 500 kilos, according to local paper La Charente Libre.