This jaw was brought back by a group of Dutch amateur paleontologists after a fossil hunt in the Ardennes, as they used to do between 1980 and 2001. The jaw was then donated to the Institute in 2016. L he himself had been sold to the Dutch by a worker from Carrières Thomas in Comblain-au-Pont, in the province of Liège, for a few beers.
Although we already know that sharks once swam in our regions, this is an exceptional discovery due to its rarity. Indeed, this cartilage from a species of prehistoric sharks, called Ctenacanthidae and whose length could reach 2.5 meters, is particularly well preserved within a rock. However, the raw sediments in which the fossil was found, mainly arkose (a type of sandstone), are generally not very conducive to the fossilization of cartilages. Analysis of these sediments, which date back to a period when the Ardennes massif was still a deep sea, enabled the research team to date the fossil.
This jaw is thus the oldest shark cartilage fossil in Europe. Similar discoveries had only been made in the United States and Australia. Teeth and backbones are the most commonly found shark elements.[display-posts orderby="rand"]
Another phenomenon that explains the rarity of such a discovery: the organization of the food chain at the time when these specimens lived. According to scientists, it seems that sharks evolved in a hostile environment and were popular prey for predatory fish and placoderms (with a kind of shell) which, themselves, could reach eight meters in length. “This is probably one of the reasons why there are so few healthy shark fossils. Many shark bodies were unable to fossilize as their populations were small and many of them ended up being eaten by predators. The shark population was under constant pressure, ”explains Sébastien Olive, paleontologist at the Royal Institute of Natural Sciences. “Their real evolution and diversification did not take place until after the disappearance of their predators in the Carboniferous era, 300 to 360 million years ago. “
Thanks to a 3D analysis of the rock in which the jawbone is located, scientists were able to determine the size of the specimen to which it belonged. “The specimen in question must have been around six feet tall. We can determine this based on the size of the lower jaw, which is 22 centimeters long and 8.5 centimeters high. “
This work was published in the American scientific journal Journal of Vertebrate Paleontology.