LIFE SCIENCE

Giant carnivorous dinosaurs had short forelimbs similar to those of tyrannosaurus rex


Meracus Dragon Skeleton Reconstruction Picture from the author

Tyrannosaurus rex (such as the famous Rex Tyrannosaurus rex) was not the only large carnivorous dinosaur with tiny forelimbs. Researchers have discovered a new dinosaur called Melaxosaurus, which had short, disproportionately short forelimbs like T. rex. On July 7, research published in Contemporary Biology suggested that T. rex and Melaxosaurus evolved short forelimbs independently and suggested some potential functions of the short limbs, such as mating or motor support.

Juan Canale, project leader at the Ernesto Bachman Paleontology Museum in Neuquén, Argentina, said: “The fossils of Meracosaurus showed areas of bones that had never been seen before, such as forelimbs and hindlimbs, which helped us understand some of the evolutionary trends and anatomy of the shark-toothed dinosaurs to which Meracosaurus belonged.”

The researchers first clarified the facts; The short limbs of the Rex Tyrannosaurus Rex were not derived from the Melax Dragon, and vice versa. Not only did the Melaxosaurus go extinct 20 million years before Rex Tyrannosaurus rex became a species, but they were also very far away from the evolutionary tree. “There is no direct relationship between the two.” Canale said. Instead, Canale argues, the short forelimbs gave the two dinosaurs some sort of survival advantage.

Canale said: “I think these proportions of short forelimbs have some kind of function. Its bones show huge muscles and fully developed shoulder girdles, so the forelimbs have strong muscles. “This means that the forelimbs were not shrunk because of its inability to function against dinosaurs.” But what exactly is its forelimb function?

Based on past research, the team identified dinosaurs like Meracosaurus and Tyrannosaurus rex with smaller heads and smaller their forelimbs. Their forelimbs are useless for hunting, as “predation-related actions are most likely done by the head.” Canale said.

Field excavation work Image from the author

Canale said: “I am more inclined to think that their forelimbs are used for other activities.” Based on the fossil record, the team was able to paint a picture of the life of the Melaks dragon before its death. This dinosaur lived in the northern region of present-day Patagonia, Argentina, aged 45 years, about 11 meters long and weighing more than 4 tons. It has a big family. “Shortly before extinction, the population flourished and reached the peak of diversity,” Canale said. Canale adds: “They may use their forelimbs for reproductive behaviors, such as holding the female during mating, or supporting themselves to stand up after resting or falling.”

The team also found that the skull of The Meracus dragon was decorated with coronal lines, grooves, protrusions and small horns. Canale said: “These ornaments appear late in development, when the individual is an adult.” The team believes these traits may be used to attract potential partners. “Sexual selection is a powerful evolutionary force. But considering that we cannot directly observe their behavior, this is impossible to be sure. Canale said.

Canale said: “These fossils have a lot of new information, and it is very well preserved.” He looks forward to exploring other questions that the Merakesosaurus fossil can help him answer. “We found a perfect location on the first day of our search, where the Melaks Dragon was found.” Canale said, “It was probably one of the most exciting moments of my career. (Source: China Science Daily Feng Lifei)

Related paper information:https://doi.org/10.1016/j.cub.2022.05.057



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