Why were carnivorous dinosaurs short-armed? A new-found species has the answers  

We humans have always been fascinated by dinosaurs. The evidence? Well, haven’t we all obsessed over movies like the Jurassic Park, at one point or the other? So, it’s no wonder that the research on these extinct species has been significantly extensive. In fact, very recently, at an excavation site in Argentina, palaeontologists have discovered the fossils of a dinosaur species whose existence have been unknown so far. Turns out, these dinosaurs had exceptionally short arms, that too disproportionate and almost identical to Tyrannosaurus. Rex (T.rex). The findings about this new species, named Meraxes gigas, have been published in the scientific journal Current Biology.  

Introducing Meraxes gigas 
Are you finding the name familiar? Well, that’s because it has been named after the fictional dragon of the same name from the Game of Thrones anthology.  

The remains of Meraxes gigas (M. gigas) have traced in the northern Patagonian region of Argentina. So far, we have come to know that the giant pre-ancient animal was 36 feet tall and weighed more than four tonnes. In fact, the skull itself was 4 feet, while the arms were only 2 feet each. And yes, if you are wondering how they managed to reach their own mouth, scientists haven’t figured that out yet! 

It has also been identified that Meraxes gigas was carnivorous and belonged to the Carcharodontosauridae group of dinosaurs called the shark-toothed lizards who existed in the Cretaceous period, almost 90 to 100 million years ago. Interestingly, this isn’t the first time the fossils of this particular species have been found. They were, in fact, first discovered in 2012! However, until recently, not much was known about their anatomy, especially shape and size of skulls, forearms and feet. So, why did it take this much time? Well, this is because, back then the complete set of fossils couldn’t be unearthed.  

Why is this discovery so important? 
You will find it interesting that not only have the scientists discovered a brand-new dinosaur species, but also found clues to the evolution and biology of similar gigantic meat-eating dinosaurs, such as the T. Rex. In fact, recent findings throw light on why these creatures had huge skulls but tiny arms. For instance, a complete forelimb among the fossils has revealed that for such a mammoth dinosaur, M. gigas did have exceptionally small arms. Likewise, a complete skull and foot have also been found, throwing light on the evolution of the group comprising of both M. gigas and T. Rex. Scientists are now even concluding that such physical characteristics might be typical of that age, and the combination of massive skulls and short arms was not only normal but also a trend.  

Interestingly, certain large-sized, long-necked herbivorous dinosaurs such as Argentinosaurus huinculensis were also found near the same excavation site. Much to the surprise of the scientists, the loose teeth found near their fossils match that of M. gigas. Okay, so what does this imply? Well, it simply means, M. gigas preyed on such herbivores. This further explains why M. gigas had such giant physical forms, considering their preys were no less big.  

Here's something even more fascinating! Turns out, M. gigas lived and died almost 20 million years before T. Rex ever walked the earth. So, what this reflect? Both the species, however similar they might be, evolved separately. In fact, recent research shows that despite having colossal heads and tiny arms, the bone structure of both the animals are significantly distinct. So, in other words, they as such have no direct relation.  

Researchers have also managed to conclude that the disproportionate physical forms of these creatures were no evolutionary accident, but offered them certain survival edges. For instance, both M. gigas and T. Rex used their heads for hunting preys, instead of their arms, as this was way more convenient to grab their food. But you will be surprised to know that although the arms were short, they were muscular; and even the chest muscles were very well-developed. Experts believe this helped them during reproduction or to support themselves stand back up after a fall. Wait, we aren’t done yet. Turns out, M. gigas also had quite an evolved skull with crests, furrows, bumps and even tiny hornlets. These were perhaps used to attract potential mates. Interesting, isn’t it?