This turtle dates back to the Jurassic period and has widened chewing bars. These probably saved the lives of descendants. Turtles with such widened chewing bars in particular survived the mass extinction to which the dinosaurs, among others, fell victim.
66 million years ago, 75 percent of all animal and plant species died out after a meteorite impact. Turtle species, however, hardly declined. Serjoscha Evers and Gilherme Hermanson from the University of Fibourg in Switzerland investigated the extent to which the survival of certain species was linked to their diet. The results were published in the journal Biology Letters.
Anatomical features on the jaw show what turtles fed on. The researchers looked at which species had hard-shelled organisms such as snails or mussels on their menu. Such animals have wide grinding surfaces in the skull and lower jaw, which are characterized by a high vascular density and an irregular bone structure. This is not found in herbivores or fish-eating turtles. Such differences exist not only in fossils, but also in today’s turtle species.
In general, only a small proportion of turtle species fed on hard-shelled organisms. But their survival rate was significantly higher during the mass extinction. 90 percent of the species persisted, while in turtles with other diets only 63 percent of the species survived.
“The specialization on hard-shelled food gave these turtle species an evolutionary advantage,” explains author Serjoscha Evers. “This is likely due to the resilience of these food sources themselves – mainly mussels and snails – to the catastrophic effects of the impact. Herbivores had difficulty surviving in the nuclear winter after the impact – with effects throughout the food chain, including carnivores. Snails and other opportunists, on the other hand, were able to survive well. So turtles, which specialized in precisely such prey, were under less pressure.”
However, the diet cannot explain everything. Many fish- and herbivorous turtle species also survived the mass extinction. So there must have been other factors that ensured that these animals could continue to exist.