The fossilized remains of a turtle found in Transylvania show that the species survived the cataclysm that eradicated the dinosaurs… will its distant descendants survive the sixth mass extinction orchestrated by Man?
Turtles are decidedly tough. An affirmation that seems obvious when we observe their particular anatomy, but their extreme resistance is not limited to their impressive shell. In any case, this is the conclusion of researchers from the University of Tübingen; in Transylvania, they got their hands on a turtle fossil which everything indicates that it survived… the asteroid which eradicated the dinosaurs.
The individual in question, whose species has been baptized Dortoka vremiri, was however not very big compared to the giant tortoises that we know. By comparing the measurements of the carapace, plastron and pelvis to those of current turtles, they were able to extrapolate and determine that it was about 19 cm long.
But above all, they were able to determine its classification. They believed it to be a member of the Pleurodira suborder. These have the particularity of having to fold their neck to the side to put their head in their shell. A very different functioning from the majority of turtles, which can simply fold their neck in the axis.
This seemingly innocuous taxonomic detail nevertheless constitutes a very interesting element for researchers once put into perspective. Indeed, they also determined that this fossil of Dortoka vremiri was about 70 million years old; but when they identified its classification, they also noticed that other representatives of the Pleurodira suborder roamed the Earth 57 million years ago, or 13 million years later.
This will not have escaped paleontology buffs: it is a time interval that contains an absolutely major event in the known history of the Earth. Indeed, it is approximately -65 million years ago that a huge asteroid probably fell on Earth, thus decimating the population of so-called non-avian dinosaurs.
A surviving species
This disaster, the dinosaurs are not the only ones to have paid the price, far from it; various studies now estimate that 65% to 80% of life on Earth has been eradicated. An observation that particularly concerns turtles… and in particular those of the family of Dortoka vremiri. “What is intriguing is that other members of the same tortoise family did not survive this event in Western Europe.”, explains Felix Augustin, PhD student at the University of Tübingen.
Therefore, a question arises: what particularity could have allowed Dortoka vremiri to escape the disastrous fate experienced by almost all his fellow creatures? To try to answer this question, the researchers looked at the local geography. Indeed, the Transylvanian basin of Haţeg, where the fossil was exhumed, was at the time a kind of island which merged with Europe only much later; Augustine therefore considered that this particular situation could have isolated them from the cataclysm.
But this hypothesis partially fell apart fairly quickly. Indeed, there is another species called Bajazidi Kallokibotion which researchers believe was also present on the island at the time. The problem is that it still disappeared at the same time as the dinosaurs. The geographical location cannot therefore explain the phenomenon on its own.
Fresh water, a post-apocalyptic eldorado
The researchers were therefore interested in the last fundamental difference between these two species: their respective lifestyles. In effect, Bajazidi Kallokibotion is a tortoise, while Dortoka vremiri belongs to the group of sea turtles. A fundamental element that could have made all the difference in their struggles for survival.
“This matches a pattern already seen in North America, that terrestrial species were significantly more impacted by this extinction than freshwater species.”details Zoltan Csiki-Sava, paleontologist at the University of Bucharest, in a press release.
Indeed, the latter had a considerable advantage in these difficult times. Indeed, the authors explain that the food chain of this environment is mainly based on the decomposition of organic matter; in contrast, the diet of land animals depends on plants, either directly in the case of herbivores, or indirectly for carnivores.
This element completely changed the situation. Because after the impact of the famous asteroid, the Earth was no longer exactly a vegetable paradise. The various numerical estimates vary considerably, and must therefore be taken with a grain of salt, but overall the finding remains the same, and it is overwhelming: the immense cloud of dust raised by the asteroid and the modification of the conditions local areas have completely decimated the flora.
This means that all the species that depended on it – including K.bajazidi – found themselves deprived of their favorite pantry. But in the water, the situation was very different; Not only did organic matter remain abundant in the water, but the quantity could even have increased following the cataclysm. While their earthly cousins had to force themselves to fast, Dortoka vremiri still had a substantial pantry which enabled him to ensure his survival.
After the asteroid, the human cataclysm
Márton Rabi, the supervisor of the study, explains that this aspect represented an advantage of freshwater species during the extinction event. This is a theory that has already been well defined for some time; however, the evidence remains scarce and insufficient to confirm the trend in statistical terms.
The case of Dortoka vremiri is one of the few concrete elements in this sense. The researchers hope that further work of this type will in the future help to identify how these species have adapted to these crisis conditions. And it’s not just basic research; work of this kind could be of particular importance in the decades to come.
Indeed, the elements that will emerge from these studies will not be limited to the specific case of this mass extinction. More generally, they could also hold clues to how freshwater species deal with ecological crises in general… which does indeed seem very important, considering that we are likely on the cusp of a climate crisis. which will continue to permanently disrupt these ecosystems.
65 million years after surviving a cataclysm that wiped out much of life on Earth, the current descendants of K.bajazidi will therefore be confronted with a new existential challenge: the sixth mass extinction, orchestrated this time by the human being himself because of his ecological unconsciousness; let’s hope that these animals will negotiate this new turn with the same skill, otherwise they could be among the many victims of the ecological disaster that seems to be looming.
The text of the study is available here.