‘Meraxes gigas’: a new species of giant dinosaur discovered in Argentina | science and technology

Argentinian, American and Canadian paleontologists have just announced a new species of giant carnivorous dinosaur – Meraxes gigas – first discovered in 2012 in Neuquén, a province in Argentina’s Patagonia region. The first comprehensive scientific study of this species has just been published in Current biologya journal that publishes original research in all areas of biology.

The species is a carcharondontosaurid theropod dinosaur, the largest predator of the Cretaceous period (90 to 100 million years ago). Like all theropods, they were bipeds with short arms and light bones. Members of this particular family of dinosaurs were the longest of theropods, measuring about 40 feet (12-13 meters) from snout to tail. One of its most distinctive features was its sharply serrated, curved teeth that resembled four-inch pruning saws (Carcharodontosaurus means shark-toothed lizard in Greek). Weighing more than four tons, “the great dinosaur eater”, as the National University of Río Negro press release dubbed it, was once one of the largest carnivorous lizards in South America.

Palaeontologist Juan Ignacio Canale, a researcher at the Argentine National Council for Scientific and Technical Research (CONICET) and the National University of Río Negro, is the main author of the Current biology article. In a Winter Patagonia video interview, Canale said it reminded her of a particular dragon. “I found this name because I like A song of ice and fire, the epic fantasy novel series that inspired the hit game of thrones TV series. “I love the names George RR Martin chose for his dragons, and this one [Meraxes] fit perfectly as both are very large reptiles with giant skulls. We also needed a new name to distinguish Meraxes of two other giant carcharodontosaurs found in Neuquén: Giganotosaurus carolinii – the “villain” of the last jurassic world movie – and Mapusaurus. It is the third of its kind, like the three dragons of A song of ice and fire“, said Canale.

Ten years of research funded by the municipality of El Chocón (the fossil-rich town of Neuquén), National geographic, and the Field Museum in Chicago (USA) preceded this dramatic announcement. Unearthing the dinosaur was quick by comparison. On the first day of fieldwork, they spotted an exposed spinal vertebra. “We started digging and more and more bones appeared. We were shocked,” Canale said. “We found a skull without a mandible, but with an intact maxilla and some teeth.” They were actually nascent teeth because unlike humans, dinosaurs and crocodiles produce several generations of teeth throughout their lives. The Neuquen Meraxes was 45 years old when it perished, making it one of the oldest carnivorous dinosaurs to have been discovered.

Almost all of the arm and leg bones were found intact, “which is very unusual because in general not much remains of the legs and arms of the largest carcharodontosaurs discovered from the mid to late Cretaceous,” said Channel. This allowed the research team to identify a new distinguishing feature of this species – a powerful claw on the inner toe that is much larger and sharper than the other two.

Meraxes giga had a skull 1.27 meters long and it is possible that it had ornaments in the snout area and around the eyes, like many other carcharodontosaurids.JORGE GONZALEZ

The hips are also distinctive. The spines on the dinosaur’s back project upward above the waist and resemble the hump on the Concavenator, discovered in 2015 in Cuenca (Spain). In another nod to the literary inspiration of the dinosaur’s name, the press release describes this part of the dinosaur as “Queen Rhaenys Targaryen’s saddle,” after the dragon ridden by the fictional queen.

The skull is another excellent specimen. As well as being huge, it is the most complete example found to date and features complex bones with protrusions, ridges and grooves. It has provided researchers with valuable information not only about Meraxes, but on all species of the family, including the famous gigantosaurus.

“It provided a lot of information about their anatomy,” Canale said. “We observed that the arms were very short, something we previously suspected, but can now say for sure since we have actual measurements.” The analysis concluded that, like other known groups of carnivores such as Tyrannosaurus and Abelisaurus, the arms shortened over time until they were only 40% the size of the femur. . Then they stopped shrinking and no one knows why. “The question is why did they reach this limit? Why didn’t the arms keep shrinking? The proportion of arms to femur is similar in all of these species,” Canale said. Like many scientific endeavours, some answers simply raise more questions.

The research team tested various hypotheses. “We observed that the pectoral girdle, where the arm, shoulder blade and other bones are inserted, is not small where the arm inserts. It is a very large and well-developed bone that encapsulates a much of the musculature that extends to the extremities. Since this musculature has to fit in somewhere, this may be the reason why the arms did not shrink further. All the musculature that came from the scapula had to be inserted somewhere. The usefulness of such short limbs is still controversial. Some believe that they were used for support during copulation, to tear prey or simply to avoid hitting the ground. But the size arms doesn’t seem so important when you have a huge skull. Meraxes gigas was just over four feet (1.27 meters) long. Other Carcharodontosaurus also had big heads, like the tyrannosaurus rex (4.6 feet or 1.40 meters) and the Giganotosaurus carolinii (5.3 feet or 1.63 meters). “What other carnivorous hunters did with their arms, these dinosaurs could do with their heads – grabbing and handling prey, pinning it down and killing it,” Canale said. Therefore, the arms would not have been very useful for eating, especially when trying to devour other giants like the argentinosaurus, one of the largest herbivores in the history of the planet. “It is certainly no coincidence that carnivores and large herbivores co-existed. There is probably a relationship with the food chain. It’s like an arms race: prey grows bigger as a defense mechanism, and their predators also grow bigger to be able to hunt them,” said the paleontologist.

Argentinian, American and Canadian scientists discovered the fossils in 2012.
Argentinian, American and Canadian scientists discovered the fossils in 2012.AKIKO SHINYA

By looking at other co-existing species, scientists can theorize about the evolutionary end of carcharodontosaurus family of dinosaurs. Specimens of two other species – Mapusaurus and Taurovenator – from the same geological period (93-96 million years ago) were discovered. “This leads us to postulate that before disappearing, they reached a maximum level of diversification. This is a group that diversified a lot just before its extinction. This is when they became extinct and were no longer the top land predators of their time in South America. Later, they will be succeeded by abelisaurids and megaraptors, but that’s another story.

The team of scientists includes Sebastián Apesteguía, Pablo Gallina, Alejandro Haluza and Federico Gianechini from Argentina; Jonathan Mitchell, Nathan Smith, Akiko Shinya and Peter Macovicky from the United States; and Thomas Cullen from Canada. The team plans to continue their research using more sophisticated techniques such as CT scans and detailed reconstructions, as they seek more answers about the bones, muscles and general anatomy of the “Ice and Fire” dragon.

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