of Montpellier scientists have studied a large number of shark and ray fossils in order to highlight the characteristics which allow a species to survive or not to a great ecological crisis.
By Hugo Hayé
The analysis of data from more than 3,200 shark and line fossils makes it possible to better understand the reasons for their disappearance or survival in the face of the fifth mass extinction experienced by the living, there are sixty- Six million years. The conclusions of this analysis carried out by Guillaume Guinot and Fabien Condamine, respectively paleontologist and biologist of evolution at the Institut des Sciences de l’Évolution de Montpellier, were published on February 24 In the Revue Science .
The details of the cataclysmic events that have caused this extinction are still debated, but one of the most commonly accepted hypotheses is the impact of a meteorite. This extinction has affected many land and sea groups, only a few of which survived. The reasons for their survival are not entirely known. This study provides some elements. Montpellier scientists have studied the evolution of the diversity of sharks and rays between – 93 million and – 56 million years. From the fossil data, the appearances of new species as well as the disappearances have been estimated.
Almost 63 % of species disappeared, the majority during an interval of 800,000 years around – 66 million years, “but we were able to demonstrate that all the groups were not equal to the This extinction: the lines show stronger extinction rates, with 72 % of extinguished species, that those of sharks, 59 % of which exhausted. We can say in this case that extinction is selective “, Indicates Fabien Condamine.
diversified diets
One of the parameters influencing the ability to survive in the face of such a crisis is the diet. Scientists sorted the species according to their diet, determined from the shape of their teeth. Almost 74 % of species with teeth adapted to the grinding of shells have turned off, potentially indicating a significant scarcity of molluscs and crustaceans which constituted their main source of food. “This is an interesting point because we know that this extinction strongly impacted the first links of the Marine Food Chain and the organizations dependent on the latter,” says Fabien Condamine.
On the other hand, those with teeth adapted to more diverse diets have done better, with almost 60 % of missing species. “In general, the living beings located in the food chain based on decaying materials have survived”, recalls Lionel Cavin, curator at the Museum of Natural History in Geneva.
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