This emerges from a new study published in the scientific journal Current Biology.
The researchers behind the study have analyzed a previously unknown predatory dinosaur, Meraxes gigas, which lived in Patagonia in southern Argentina about 90-95 million years ago. It was not one of the largest carnivores of this time but still a terrible beast with a weight of about four tons.
In body shape it was very similar to T. rex with massive hind legs, very large head, a huge gap – and pitiful arms.
Surprisingly similar
The researchers note that in principle all very large predatory dinosaurs had such proportions, even though they belonged to different families that were not closely related to each other. Meraxes gigas belonged to the family Carcharodontosauridae, for example, while T. rex belonged to the family Tyrannosauridae.
The question is why they were so similar. Researchers have been researching the problem for over 100 years and have put forward a long list of more or less strange hypotheses about what the arms may have been used for – without finding answers. But the skeleton of Meraxes, which is unusually complete, has provided clues that could solve the mystery.
The head took over the role of the arms
Using all the data from the study, the researchers found that all giant predatory dinosaurs, regardless of origin, had a very similar growth. As they developed, their heads became, proportionally, larger and at the same time their arms shrank more and more.
The bottom line is that it probably does not make sense to speculate about the function of the arms.
– The arms were reduced as an effect of the head becoming more massive. Their function became completely secondary because the head was optimized so that the animal could overpower large prey animals, says the leader of the study, Peter Makovicky see University of Minnesota i USA.
It all results in the arms becoming unnecessary when evolution focused everything on jaws, teeth and bite strength.
The predatory dinosaurs, Theropoda, is a suborder that includes all carnivorous species among the dinosaurs. All known species were bipedal and had a very characteristic appearance with powerful hind legs, shorter arms and relatively large heads with powerful jaws. Allosaurus, Ceratosaurus, Carcharodontosaurus and Tyrannosaurus were all very large with weights of several tons, while Velociraptor and Deinonychus were smaller.
The Theropods originated 231 million years ago and became extinct 66 million years ago. But in the strict sense, they still live today because they gave rise to the birds of our day. Sparrows and crows are in descending order descendants of small predatory dinosaurs that began to develop into birds about 160 million years ago.
Source: Current Biology.
Source: TT
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