Scientists have uncovered the world's longest dinosaur tracks sprawling over more than 150 meters, that were left 150 million years ago by a dinosaur at least 35 metres long and weighing 35 tonnes.
The tracks were discovered in the French village of Plagne in 2009, and were identified as the world's largest dinosaur tracks.
Scientists from The National Center for Scientific Research (CNRS) and the Pterosaur Beach Museum supervised digs at the site, a meadow covering three hectares.
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 reveals 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 metres when including the mud ring displaced by each step.
The footprints reveal five elliptical toe marks, while the handprints are characterized by five circular finger marks arranged in an arc.
Biometric analyses suggest the dinosaur was at least 35 metres long, weighted between 35 and 40 tonnes, had an average stride of 2.80 metres, and travelled at a speed of four kilometres per hour.
It has been assigned to a new ichnospecies Brontopodus plagnensis.
Other dinosaur trackways can be found at the Plagne site, including a series of 18 tracks extending over 38 metres, left by a carnivore of the ichnogenus Megalosauripus.
The researchers have since covered these tracks to protect them from the elements. However, many more remain to be found and studied in Plagne, they said.
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