In the French village of Plagne, in the Jura Mountains, 200 kilometers east of Lyon, there is a set of huge footprints made 150 million years ago. The footprints belonged to a sauropod, the largest class of dinosaurs, that had very long necks, which helped them reach the foliage on top of tall trees, long tails and four thick, pillar-like legs. An adult sauropod easily weighed 100 tons, although this particular individual probably weighed about 35 tons.

Back then, this region was a warm and shallow sea, dotted with small islands. When the sea got low, all kinds of dinosaurs waded through the marsh as they hopped from island to the next in search of food. One could almost imagine this large sauropod walking quietly on the beach leaving thick footprints in the mud, that got subsequently covered by sediments. Tectonic upheaval raised the landmass and exposed the footprints for humans to discover.

Dinosaur trackways have been discovered in many parts around the world. What makes this particular tracks interesting is they are the longest tracks to be discovered belonging to the largest class of dinosaurs. The tracks run for a length of 155 meters and has 110 individual footprints. Analysis of these tracks suggest that the prints were left by an animal at least 35 meters long and weighing more than 35 tons, that traveled about 4 kilometers per hour with an average stride of 2.8 meters. What’s more— this sauropod was a previously unknown species that has now been named Brontopodus plagnensis, which translates as “thunderfoot of Plagne”.

Artists impression of a Brontopodus plagnensis.