T. Rex wasn’t the only dinosaur with small arms!

That’s awful Tyrannosaurus Rex Consoling himself, he’s not the only large predator with ridiculously small arms. Discovery Miraxis Gegaspresenting the same characteristics, however raises the question of this morphological convergence, despite the distance between the two species on the phylogenetic tree.

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in between dinosaurs Carnivorous giants, tyrannosaurs feature ridiculously disproportionate arms compared to the rest of the body. However, a team of scientists discovered a new species of dinosaur with the same morphological peculiarity. It’s about Miraxis Gegas. Even more surprising is that this new dinosaur had nothing to do with tyrannosaurs. The two species could have evolved completely independently towards A Morphology The like, which raises the question of the origin of this characteristic and his interest.

New skeleton discovered in Patagonia

The Miraxis Gegas It belongs to the group of Carcharodontosaurids, which lived at the beginning of the Cretaceous period, that is, from about 129 to 89 million years ago. Carcharodontosaurids are among the largest terrestrial predators in existence, such as Giganotausorus where is the Tyrant, for example. But not another known predator, The Tyrannosaurus Rex, which is part of a different group. Despite its characteristics physical relatively close, Mr. Gigas And the T-Rex They did not live at the same time at all, Mr. Gigas After disappearing about 20 million years before the appearance of T-Rex. The two are quite far fromTree of evolution and not directly related. The fact that there are weapons so small that they are not attached to the transmitter hereditaryHow do we explain that such a morphology exists in these two species?

. skeleton Miraxis Gegas Recently discovered in northern Patagonia (Argentina) can give some clues. The fossil discovered belonged to an adult male, 45 years old, 11 meters long and probably over five tons. The skeleton is particularly complete at the level of the arms and legs and shows the presence of large muscular insertions as well as a highly developed pectoral girdle. my arm Miraxis Gegas So it was small but powerful. An important fact because it means that this conformation is not the result of fade away Gradual reduction of the upper extremities due to their uselessness. Despite their size, these little arms had to be used for something.

Genetic specificity linked to head size?

For Juan Ignacio Canal, lead author of a study published in the journal current biologyAnd the Mr. GigasSuch as T-Rex, its small arms can be used during breeding, in particular to hold the female during mating. Other theories suggest that it could have been useful for getting up after a fall. However, it is currently impossible to have any certainty about its exact usefulness.

However, none of these theories explain why these giant monsters’ arms were so short. For Juan Ignacio Canal, it could be the result of genetic selection related to head size, and the two components appear to be closely related. Indeed, researchers have noted that, in general, among large predators such as Mr. Gigas And the T-RexThe larger the head, the smaller the arms.

Thus it appears that in these dinosaurs, a large head indicates a negative interaction with the length of the arms. In large predators, Big head being an asset And certainly it was a breed standard, he actually chose individuals with small arms. A new path to dig.

The fossil also provides other valuable information about the social life of Miraxis Gegas And on the importance of the head in this genre. The Skull It is already decorated with many “ornaments”: spurs, protrusions, grooves and small horns, characteristics that are found only in adult individuals. Hence the hypothesis that these cranial motifs certainly played a role in male sexual attractiveness.

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