Science

The largest turtle ever

There was probably never a bigger turtle on earth: 1145 kg and with one Tanks of 2, 40 meters long, Stupendemys geographicus swam through the rivers and lakes until five million years ago South America. Edwin Cadena from the Universidad del Rosario in Bogotá, the capital of Colombia, and his colleagues in the journal Science Advances appreciate this.

These freshwater turtles were almost twice as heavy as the largest ones today relatives still alive: leatherback turtles that live in the warmer seas up to the coasts of Scotland and have a weight of 650 Develop kilograms and a tank of 2, 13 meters. There are only three larger reptile species today, all of them crocodiles like the six-meter-long and one-ton inguinal crocodile.

Giant turtle because of giant crocodiles

Such giant crocodiles were probably the reason for the growth of the turtle Stupendemys geographicus. Because crocodiles up to ten meters long lived in the same waters at the time, only large turtles could survive their attacks, the researchers suspect. The discovery of a crocodile tooth and bite marks in the shell of various giant freshwater turtles suggest this conclusion.

The giant growth of the freshwater turtles is not completely surprising: “Already 1976 Stupendemys geographicus was described for the first time on the basis of finds in Venezuela, ”says turtle specialist Uwe Fritz from the Museum of Animal Science of the Senckenberg Natural History Collections in Dresden.

Das Forschungsteam um Edwin Cadena (rechts) hat nicht nur in Kolumbien, sondern auch im Norden Venezuelas Fossilien einer riesigen Schildkröte ausgegraben.

The research team around Edwin Cadena (right) has found fossils not only in Colombia but also in northern Venezuela of a huge … Photo: Edwin Cadena

Since then, only parts of the tank of this type have been found in South America, with for which the researchers classify the animals as huge, but could hardly estimate their exact dimensions.

In the past few years, Cadena's team has been located near Urumaco in the northwest of Venezuela and in the Tatacoa- Desert in the south of Colombia a few more, partly complete tanks and a lower jaw of this type and analyzed them “very carefully”, says Uwe Fritz, who was not involved in the investigations.

Horns on the tank – for defense or to boast

In addition to the record size, the research team also found another Peculiarity of the extinct turtle species: From the shell of Stupendemys geographicus, two roughly grow to the right and left of the opening from which the turtle sticks its head. centimeters long horns to the front. These extensions were similar in shape to cows and could have been used to defend against attackers and to protect the particularly vulnerable neck.

Instead of pulling the head back into the tank in the event of danger, this turtle species placed it under the side of the tank. This is still the case today with species of the “neck-turning turtle” genus, some of which still live in the inland waters of South America, Australia, New Guinea, Madagascar and Africa. This behavior protects the skull, but the neck is not, so horns would have been effective protection.

[Mehr zum Thema Riesenschildkröten hier und im Video: Riesenschildkröten wiederentdeckt]

If this hypothesis is correct, then probably all animals should have had such horns, whereas Cadena's team has only had them so far found three particularly large specimens. The alternative hypothesis of the South American researchers is therefore that each of them could have been males who could have fought against their rivals with such bullhorns. “Maybe the animals just impressed their rivals and the male with the largest horns won this competition,” says Fritz.

Wo heute nur noch Wüste ist, war vor fünf Millionen Jahren noch ein Netz von Flüssen und Seen, in denen neben Riesenschildkröten auch Riesenkrokodile lebten.

Where there is only desert today, there was a network of rivers and lakes five million years ago, in which in addition to giant turtles … Photo: Edwin Cadena

The habitat of the giant tortoise in South America consisted of a huge water system made up of swamps, lakes and slowly flowing rivers. The turtles presumably grazed the bottom of these waters and fed on hard-shelled animals that they could break open with their mighty jaws, write Cadena and his colleagues.

The turtles supplemented this food similarly to theirs relatives probably with the high-energy fruits of palm trees and other plants. Since the giant tortoises swallow very large fruits and their seeds could be excreted from some distance away, Stupendemys geographicus probably had an important distribution role in the ecosystem.

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