In 2008, a couple of naturalists found near Plagne, a small town nestled in the Jura massif in eastern 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) and the Claude Bernard University of Lyon confirmed the finding and determined that the trail, which extended for about 155 meters , had been left behind by a sauropod, which 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 through that area at that time stood out even among its relatives.
From the tracks – depressions 1.50 meters in diameter stamped in a calcareous layer – the experts suggested at first that they had been left by a specimen that must have been around 25 meters long and about 30 tons in weight. . Now, a comprehensive study of the markings indicates that it was much larger, some 35 meters long and 35 to 40 tons, which would make it one of the most formidable land animals known.
The work, published in the Geobios magazine by scientists from the aforementioned CNRS and the Pterosaur Beach museum in Crayssac, has also confirmed that it is the largest set of this type of footprint found to date, made up of 110 footprints. . Biometric analysis of them has allowed them to establish that the specimen was moving at a speed of about 4 kilometers per hour, with an average stride length of 2.80 meters . The front ones have five impressions arranged in an arc, corresponding to the fingers, and the rear ones, another five, more elliptically shaped. Paleontologists have named this new ichnospecies – a classification that takes into account the fossilized activity of a living being – Brontopodus plagnensis .
Island paradise
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 with 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 movements of these giants and their migration from the mainland.
Other traces have also been found at the site, among which a set of 18 footprints that cover about 38 meters and that belonged to a predator stands out. Today, these remains are conveniently protected to be able to be studied in greater detail. Furthermore, the researchers are convinced that there are still many traces to be discovered and analyzed in the surroundings of Plagne.
Reference: The dinosaur tracksite of Plagne (early Tithonian, Late Jurassic; Jura Mountains, France): The longest known sauropod trackway . Jean-MichelMazin et al. Geobios . Volume 50; number 4. August 2017. Pages 279-301. https://doi.org/10.1016/j.geobios.2017.06.004
Images: P. Dumas / A. Bénéteau; Dinojura
