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Palaeontology

Jurassic tracks

Work has begun on an extraordinary palaeontological site discovered this past June in the forests of the Jura mountains. There, in abandoned quarry, researchers are busy investigating hundreds of dinosaur footprints.

Just a few months old, this discovery already has researchers working around the clock, on the trail of dinosaurs that roamed the area approximately 150 million years ago. Sauropods, which were large herbivorous dinosaurs (9 to 21 m long), have left their mark near the small village of Loulle, sure to become an international palaeontological showcase. Hundreds of these giant animals' footprints (possibly over a thousand), have recently been discovered scattered over a 3 km2  area. The on-site researchers, led by Jean-Michel Mazin, from the PEPS lab1 already have their work cut out: Their first job is to clean up, photograph, and then digitize this exceptional site. This could help researchers learn more about these peaceful giant herbivores, possibly the largest animals to have ever roamed the earth. These “heavy-weights”–weighing at least ten tons–had very long necks that let them both snatch leaves from tree tops and graze down below. The little information we have about them was gathered in a few areas where diplodocus–the best known member of the sauropods–left traces, mainly in North America, in Colorado and Utah. But it turns out that the diplodocus, or rather its sauropod cousins, also came to Europe, to the Swiss Jura. We might now assume that they crossed over into France near Loulle, the place where the footprints were found.

The discovery actually dates back to 2005, when a jogger with a sharp eye spotted an odd-looking footprint near an abandoned limestone quarry in the middle of the forest. He immediately informed the Jura Heritage Conservation authorities. “Hikers often call when they see something of natural value. It often is of no particular interest, but once in a while, it's a windfall,” Mazin observes. Once on the spot, the researchers didn't have a moment's doubt: “It took us just a few seconds to be absolutely sure. These were definitely the footprints of the European cousins of the diplodocus.”

 

tracks

 

The team started making observations and measurements, as a first step in estimating the  site's importance. All the footprints formed indentations in the ground that were between

20 cm and 1 m in diameter (showing the ages of the animals–from very young to very old), with a rim formed where sediment had been expelled and then dried. The site soon began to take on an exceptional quality. The researchers counted over 500 footprints, which had certainly been uncovered during the exploitation of the quarry over 30 years ago, but which no one had noticed. By extrapolating these findings to the rest of the site, they reckoned that there were approximately 1500 footprints, signaling the passing of a herd of adult and young sauropods. Did these giant creatures regularly pass through the Jura? “Certainly, because the footprints are very close together, as if the sauropods had continuously traveled back and forth through there,” Mazin believes. One astonishing detail is that the researchers are able to follow the trails of several individuals for only dozens of meters. What happened to them then? Researchers believe that they will be able to solve this mystery once excavations get under way. Yet this palaeontological treasure trove has already yielded some invaluable clues as to the environment of the time. “Reconstructions all show that land in the area was totally submerged 150 million years ago,” Mazin explains. “But these footprints let us refine such reconstructions, by showing that, although most of the Jura was under water, there must have been small islands that emerged.” And this discovery is an important part of the puzzle, given that specialists have very little detailed information about past environments.

Loulle promises to be a world-class palaeontological deposit, comparable to the deposits in the US. To preserve and best use this heritage, the team has embarked on a far-reaching program with the help of the relevant authorities and organizations: the Jura departmental council, the Franche-Comté region, and the municipal authorities of the Loulle area. Once the excavations and geological and palaeontological work is over, the scientists would like to place the site under physical and legal protection. Mazin also wants to share the discovery with the next generation, which will be responsible for site preservation in the future, “through educational projects, for instance, or perhaps even a museum.” An appropriate way of celebrating our reunion with these gentle giants from the distant past.

 

Azar Khalatbari

Notes :

1. Paléoenvironnements et paléobiosphère (CNRS / Université Lyon-I).

Contacts :

Peps, Villeurbanne.
Jean-Michel Mazin
jean-michel.mazin@univ-lyon1.fr


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