London, Nov 14 (IANS) The world's longest dinosaur tracks discovered in the French village of Plagne were left 150 million years ago by a dinosaur that was at least 35 metres long and weighing no less than 35 tonnes, new research has found.
The dinosaur named Brontopodus plagnensis had an average stride of 2.80 metre, and travelled at a speed of four kilometres per hour, said the study published in the journal Geobios.
The research was conducted by scientists from the Laboratoire de Goologie de Lyon, the Laboratoire Magmas et Volcans and the Pterosaur Beach Museum in France.
When the sauropod tracks were discovered in the French village of Plagne -- near the southeastern city of Lyon -- in 2009, the news went round the world.
Between 2010 and 2012, researchers from the Laboratoire de Geologie de Lyon supervised digs at the site. Their work unearthed many more dinosaur footprints and trackways.
It turns out the prints found in 2009 are part of a 110-step trackway that extends over 155 metres -- a world record for sauropods, which were the largest of the dinosaurs.
Dating of the limestone layers revealed that the trackway was formed 150 million years ago, during the Early Tithonian Age of the Jurassic Period.
At that time, the Plagne site lay on a vast carbonate platform bathed in a warm, shallow sea.
The presence of large dinosaurs indicates the region must have been studded with many islands that offered enough vegetation to sustain the animals.
Land bridges emerged when the sea level lowered, connecting the islands and allowing the giant vertebrates to migrate from dry land in the Rhenish Massif.
Additional excavations conducted as late as 2015 enabled closer study of the tracks.
Those left by the sauropod's feet span 94 to 103 centimetre and the total length can reach up to three meters when including the mud ring displaced by each step.
The footprints reveal five elliptical toe marks, while the handprints are characterised by five circular finger marks arranged in an arc, the study said.
Biometric analyses showed that the dinosaur was at least 35 metres long and weighed between 35 and 40 tonnes.