In 2008, a couple of naturalists found near Plagne, a small town nestled in the Jura massif, in the east of France, an extraordinary set of footprints that seemed to belong to a large dinosaur. Shortly thereafter, a team of researchers from the French National Center for Scientific Research (CNRS, for its acronym in French) and the Claude Bernard University in Lyon confirmed the finding and determined that the trail, which stretched for about 155 meters, had been left by a sauropod that inhabited the region 150 million years ago. Some of these animals, whose long necks and tails give them a characteristic appearance, could reach enormous dimensions, but the one that walked at that time in that area stood out even among their relatives.
From the footprints – some depressions of 1.50 meters in diameter stamped on a calcareous stratum – the experts suggested at first that they had been left by a specimen that should have been around 25 meters long and weighing 30 tons. Now, an exhaustive study of the marks indicates that it was much greater, of about 35 meters in length and of 35 to 40 tons, which would turn it into one of the most formidable terrestrial animals known.
The work, published in the magazine Geobios by scientists of the aforementioned CNRS and the museum The beach of the pterosaurs, in Crayssac, has confirmed, in addition, that it is the largest set of this type of footprints found to date, consisting of 110 footprints . The biometric analysis of them allowed them to establish that the specimen was traveling at a speed of about 4 kilometers per hour, with an average length of stride of 2.80 meters. The front ones present five impressions arranged in arc, corresponding to the fingers, and the later ones, other five, of more elliptical form. Paleontologists have called this new icnospecies-a classification that takes into account the fossilized activity of a living being- Brontopodus plagnensis.
During the Titonian, at the end of the Jurassic, the area was bathed by a warm and shallow sea. However, the presence of such large dinosaurs indicates that it must have been dotted by numerous islands covered with enough vegetation to guarantee the sustenance of these herbivores. When the water level dropped, they were connected by natural land bridges, which favored the displacement of these giants and their migration from the mainland.
Other traces have also been found at the site, including a set of 18 footprints that cover about 38 meters and that belonged to a predator. Today, these remains are conveniently protected to be studied in greater detail. Moreover, the researchers are convinced that there are still many traces to be discovered and analyzed in the vicinity of Plagne.