It is known that the king of dinosaurs, Tyrannosaurus rex, had tiny arms.
But it turns out the species may also have evolved narrower eye sockets than their ancestors so they can bite harder.
While in many animals — and most dinosaurs — the eye socket is just a circular hole in the skull that houses the eyeball, it’s very different in large carnivores.
In a new study, University of Birmingham researchers show that the unusual elliptical or oval eye sockets found in the skulls of these predators may have evolved to help their skull absorb the impact when they pounce on prey .
They suggest that the evolution of narrower orbits may have reduced the space available for eyeballs in theropod skulls, but allowed more room for jaw muscles and improved the robustness of their skulls.
King of the Dinosaurs: T.Rex may have evolved narrower eye sockets than their ancestors so they can bite harder, experts say. They compared a cranial and life reconstruction of T.Rex with its original eye socket and eye (left) to a hypothetical reconstruction with a circular eye socket and enlarged eye (right) to measure forces during bite simulations
Computer simulations of hypothetical dinosaur skulls. Colors indicate skull stress. High stresses occur in a skull with a round eye socket (above), lower stresses in a skull with a keyhole-shaped eye socket (below).
WHAT WAS T.REX?
Tyrannosaur Rex was a type of bird-like, carnivorous dinosaur.
It lived 68 to 66 million years ago in what is now western North America.
They could grow up to 12 meters long and 4 meters high.
More than 50 fossilized specimens of T.Rex have been collected so far.
The monstrous beast had one of the strongest bites in the animal kingdom.
An artist’s rendering of T.Rex
This may have helped them bite harder at the expense of adapting to larger eyes, which previous research has suggested to improve visual perception.
dr Stephan Lautenschlager, lecturer in paleobiology at the University of Birmingham and author of the new study, analyzed the shape of the orbits of 410 fossil reptiles from the Mesozoic Era (252 to 66 million years ago).
This included dinosaurs and their close relatives like crocodiles.
He found that most species, especially herbivores, had circular eye sockets.
However, large carnivores with skulls longer than 1 m often had elliptical or keyhole-shaped eye sockets as adults, although as juveniles they had more rounded eye sockets.
The researchers found that ancient species tended to have circular eye sockets compared to newer species, with large theropods having more keyhole-shaped eye sockets than their ancestors.
These observations suggest that larger carnivorous species evolved keyhole-shaped eye sockets over time, but that they evolved this shape as adults, not juveniles.
“The results show that only some dinosaurs had elliptical or keyhole-shaped eye sockets,” said Dr. Lautenschlager.
“But all of these were large, carnivorous dinosaurs with skulls 1m or more in length.”
To investigate the influence of orbital shape on skull structure and function, researchers compared the forces experienced by a theoretical model reptile skull with five different orbital shapes during bite simulations.
They found that a skull with a circular eye socket was more susceptible to high biting loads.
However, when these were replaced with other orbital shapes, the stresses were significantly reduced. Experts hypothesized that this allowed top predators, including T.Rex, to develop high bite forces without compromising skull stability.
In comparison: the skulls of various dinosaurs are shown, showing different shapes of the eye sockets
Narrower eye sockets may have helped T.Rex bite harder at the expense of adapting to larger eyes, leading previous research to suggest that visual perception may be improved
The study also showed that most herbivorous species and young large dinosaurs retained a circular eye socket.
Only large adult carnivores took on other morphologies, such as B. elliptical, keyhole-shaped or eight-shaped eye sockets.
dr Lautenschlager added: “In these species, only the upper part of the orbit was actually occupied by the eyeball.
“This also resulted in a relative reduction in eye size compared to skull size.”
The researchers also looked at what would have happened if eye size had increased at the same rate as skull length.
In this scenario, T.Rex eyes would have been up to 30 cm (11 in) in diameter and weighed nearly 20 kg (44 lbs), instead of an estimated 13 cm (5.1 in) and 2 kg (4 .4 lbs).
The study was published in the journal Communications Biology.
HOW DINOSAURS WENT EXTINCT AROUND 66 MILLION YEARS AGO
Dinosaurs ruled and dominated the Earth about 66 million years ago before suddenly becoming extinct.
This mass extinction is known as the Cretaceous-Tertiary extinction.
For many years it was believed that climate change was destroying the giant reptiles’ food chain.
In the 1980s, paleontologists discovered a layer of iridium.
This is an element that is rare on Earth but found in large quantities in space.
When this was dated, it coincided exactly with the time when dinosaurs disappeared from the fossil record.
A decade later, scientists discovered the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, dating from the period in question.
The scientific consensus now says that these two factors are linked and both were likely caused by a giant asteroid crashing into Earth.
With the projected size and impact speed, the collision would have created an enormous shock wave and likely triggered seismic activity.
The fallout would have created plumes of ash that likely covered the entire planet, making it impossible for the dinosaurs to survive.
Other animal and plant species had a shorter span of time between generations, which allowed them to survive.
There are several other theories as to what caused the demise of the famous animals.
One early theory was that small mammals ate dinosaur eggs, and another proposes that toxic angiosperms (flowering plants) killed them.