A new species of huge dinosaur estimated to measure more than 100ft long has been found amid a lost world of fossil remains.

Palaeontologists unearthed the remains of the creature, Futalognkosaurus dukei, in Patagonia, Argentina, in a 400sq m (4,300sq ft) area that was a dinosaurs’ graveyard. The plant eater was the height of a four-storey building and is among the three biggest dinosaurs discovered.

More than 1,000 other animal and plant remains were found near by, including dinosaurs, ancient fish, at least two crocodile-like animals and 300 teeth.

Several dinosaurs were uncovered besides Futalognkosaurus dukei, including a flying pterosaur and a carnivorous megaraptor.

The wealth of finds, including leaves that show what the dinosaur ate, has given scientists unprecedented insights into the ecosystem of the area in the Upper Cretaceous period, from 97 million to 66 million years ago.

At least 240 fossils of plants have been unearthed since the site was discovered on the banks of Lake Barreales in the Argentine province of Neuquén in 2000.

Alexander Kellner, of the Brazilian National Museum, said: “As far as I know, there is no other place in the world where there is such a large and diverse quantity of fossils in such small area. That is truly unique.

“The accumulation of fish and leaf fossils, as well as other dinosaurs around the find, is just something fantastic. Leaves and dinosaurs together is a great rarity. It’s like a whole lost world for us.”

Many of the remains are thought to have been preserved because the dinosaur’s body blocked a waterway, creating a logjam of dead animals and plants. Marks on the fossilised skeleton indicated that it was partially eaten by predators or scavengers before washing into a slow-moving river.

An estimated 70 per cent of the skeleton has been found. It is more usual for only 10 per cent of mega-herbivores to be recovered.

The creature was calculated to be 32-34m (105112ft) with the neck being 17m long. The tail was estimated at 15m. The excavated spinal column weighed eight tonnes and one of the neck vertebra was about 1m high.

Jorge Calvo, the director of Coma-hue National University Palaeontology Centre, said: “This is one of the biggest in the world and one of the most complete of these giants.”

Jeff Wilson, of the University of Michigan, reviewed the findings, reported in the Annals of the Brazilian Academy of Sciences. He said: “I should really try to underscore how incredible it is to have the partial skeleton of something this size. It shows us the upper limit for dinosaur size. There are some that are bigger but they all top out around this size.”

The other two largest dinosaur skeletons found were also in Patagonia – Argentinosaurus, at about 35m long, and Puertasaurus reuili, at 35-40m.

The name Futalognkosaurus, meaning giant chief of the lizards in the native Mapuche language, was chosen in honour of the indigenous population and dukei was selected because the dig was paid for by the Duke Energy Argentina company.

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