powerful jaw Tyrannosaurus Rex They held together with such force that they would split the bones of dinosaur prey.But for such a powerful bite, the king Dinosaur had to do one Evolution Tradeoff: It has to accommodate smaller eyes.
Based on an analysis of 410 fossil specimens of reptiles from the Mesozoic Era (2.52 to 66 million years ago), one scientist concluded: Tyrannosaurus Rex Over time, other similar carnivores had smaller, narrower eyes, possibly to compensate for their increasingly powerful bites. In particular, carnivores with skulls longer than 3.2 feet (1 m) tend to have slender, keyhole-shaped eye sockets or sockets as adults, while young carnivores and herbivores of all ages have rounded eye sockets.
“It makes sense, of course; as predators get bigger, they turn to larger prey, which requires greater bite force to address,” said Stigwall, Senior Curator of Vertebrate Paleontology at the National Museum of Scotland Stig Walsh was not involved in the study. Juvenile carnivores.
The new study was published Thursday (August 11) in the journal communication biology (opens in new tab)support the idea brain Sensory organs such as the eyes must adapt to the animal’s primary feeding strategy, Walsh told Live Science in an email.in this case Tyrannosaurus RexThis feeding strategy revolves around a broken bone.
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For the analysis, study author Stephan Lautenschlager, a vertebrate paleontologist at the University of Birmingham, UK, scoured the existing literature for descriptions of dinosaur and reptile skulls dating back to the Mesozoic. From these, he selected hundreds of skulls with original preserved eye sockets, as well as a handful of incomplete skulls whose eye sockets could be reconstructed with “a great degree of confidence”.
410 specimens include a wide variety of species, from crocodiles to hulking herbivores such as Triceratops Carnivorous theropods such as Tyrannosaurus Rex and Tyrannosaurus Batata tyrannosaur relative with an equally massive skeleton and slender arms.
When comparing all these skulls, Lautenschlager found several patterns: Most creatures, especially herbivores, have rounded eye sockets. However, as you moved through the Mesozoic, the orbital shapes of the big-headed carnivores began to evolve into ovals and keyhole-shaped openings.
Juvenile specimens of some of these carnivores – including Tyrannosaurus Rex and T.bataar — suggesting that dinosaurs developed these squashed eye sockets in adulthood, while they retained round eye sockets in their youth. “Obviously we don’t have growth series for many species, but for the ones we do have, to me, that makes the reason for the shape changes we’re seeing related to feeding,” Walsh noted.So as a young man Tyrannosaurus Rex Getting bigger, so did its prey, and its bite force had to increase to adapt.
To understand how these eye socket shapes affected the dinosaur’s ability to chew bones, Lautenschlager designed three computer models, each more complex than the last.
The first and simplest model is a flat plate with various eye socket shapes carved into it – think how rivets help distribute force through a solid steel plate. “The location and shape of the holes have an impact [on] How stress and deformation propagate through the plate, Lautenschlager told Live Science in an email.The final and most complex model is a digital model Tyrannosaurus Rex skull. “As the stereotype of large carnivorous theropods with extremely narrow orbits, [T. rex] ideal for testing the effects of orbital shape in actual dinosaur species,” Lautenschlager said.
These models show that keyhole-shaped sockets deform much less than round sockets during simulated occlusion because they direct the occlusal force to the strong bone behind the sockets. “The keyhole shape reduces and redirects stress in the skull during occlusion better than circular orbits,” Lautenschlager said. “This is clearly an adaptation found in many large carnivores in different groups. Something that evolved independently.”
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If, on another timeline, Tyrannosaurus Rex Having never evolved an elongated orbit but rather a round shape, the dinosaur’s eyes weighed nearly 44 lbs (20 kg) and were 11.8 inches (30 cm) wide, instead of the estimated 4.4 lbs (2 kg) and 5.1 inches (13 cm) ), model recommendations. Thus, a round eye socket can support an eye approximately seven times the volume of a keyhole socket.
with such big eyes metabolism expensive Tyrannosaurus Rex And it doesn’t match what we know about dinosaur brains, Walsh said. “The retina is a product of a region of the brain called the diencephalon, one thing we know about large predators Tyrannosaurus Rex is their size The brain can’t keep up with the rhythm As they grow throughout their lives, their body size,” he said. So if Tyrannosaurus RexThe size of their eyes has kept pace with their overall skull size, and the areas of the brain that process vision also need to get larger.
It’s worth noting that while this new study provides strong clues about the dinosaur’s overall eye size, the fossil bones cannot reveal details of the eye or associated soft tissue anatomy, such as nerve and muscles.
“This is [where] “We’re at an impasse in paleontology because we can hardly tell the actual shape of the eyeball from fossil bones,” Lautenschlager said. “Some dinosaur species may have had special eyes similar to modern birds.” Owls, for example, The eyes are elongated and barrel-shaped.The eye, the shape of which affects how light hits the retina; currently, we cannot tell the exact shape of the eye Tyrannosaurus RexHe says.
In follow-up studies, it would be interesting to extend Lautenschlag’s orbital shape analysis to include birds, The only living offspring of dinosaurs, and mammals with powerful bites, Walsh said. “Maybe mammals with high bite force evolved a different way to de-stress in reptiles — that needs to be investigated,” he said.
Originally published on Live Science.