Why not come face to face with the world’s most fearsome dinosaur? Let’s poke fun at where it’s most sensitive: its tiny little arms.
Scientists have long debated the reasons behind the tyrannosaurus rex’s small limbs. While they agree that these arms were nearly useless, the evolutionary triggers for their size have remained a mystery—until now.
New research conducted by University College London (UCL) and the University of Cambridge analyzed 82 species of theropods, a group of bipedal, primarily carnivorous dinosaurs. The study revealed that as the head and jaw of the tyrannosaurus grew larger, the arms became progressively smaller.
This indicates that tyrannosaurus and other predatory dinosaurs evolved to rely on their powerful jaws and heads for hunting rather than their claws. Consequently, their arms diminished over time, eventually appearing disproportionately small compared to their massive heads and bodies, leading to a plethora of jokes about their little arms.
Researchers have long recognized that while tyrannosaurus rex‘s arms are vestigial—having lost their original function—this newfound correlation between arm reduction and head enlargement marks a significant development in our understanding.
The study published in Proceedings of the Royal Society B discovered that smaller arms correlate more strongly with the evolution of large, powerful skulls and jaws than with the dinosaur’s overall size. This means that having smaller arms isn’t simply a matter of size.
As lead author Charlie Roger Scherer, a PhD student in UCL Earth Sciences, puts it: “The head replaced the arm as the primary method of attack. It’s a ‘use it or lose it’ scenario; if the arms aren’t useful, they will eventually shrink.”
He adds, “These adaptations often occurred in environments rich in large prey. Trying to grab a 100-foot-long sauropod with claws is impractical. Instead, attacking and restraining it with powerful jaws would have been much more effective.”
Interestingly, while we commonly associate small arms with tyrannosaurus, there were several other theropods that skipped out on upper-body workouts. For instance, the Carnotaurus had even smaller arms than the tyrannosaurus.
Regardless of size, the study indicates that some smaller theropods also had similarly potent heads and tiny limbs, highlighting the adaptability of these fascinating creatures.
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Source: www.sciencefocus.com
