7/2/2023 0 Comments Big eyeballsAnd the biomechanical stress and strain model that Lautenschlager used “assumes the skull is a single homogenous unit, which is far from reality.” Although this model does not account for joints and muscles in and around bones, O’Connor says, it is still widely used in paleontology because there is no good alternative. “If you take a circular in a flat skull and stretch the skull so it is taller, then the orbit becomes oval,” she says. Paleontologist Jingmai O’Connor of the Field Museum in Chicago, who also wasn’t involved in the study, is not entirely convinced of this diet-based explanation and suggests a dinosaur’s size may have played a large role. “Based on the data presented, it seems to be a compelling explanation that sort of this combination of body size and diet,” Irmis says. Other smaller or herbivorous archosaurs would similarly not need strangely shaped eye sockets. rex, you could easily get away with circular eye sockets because “you’re eating small prey, your body size is small, you’re not facing the same functional constraints that the adult is,” he says. This change supports the hypothesis that eye-socket shape might be based on the power of an animal’s bite, says Randy Irmis, curator of paleontology at the Natural History Museum of Utah, who was not involved in this work. rex grew into an adolescent and eventually reigned supreme in its ecosystem, the animal’s eye sockets became keyhole-shaped. “I think that’s a general theme throughout the animal kingdom,” Lautenschlager says. rex would gaze up to a parent with big, round eyes. Much like infant animals today, a baby T. rex’s eye socket changed over its life span, starting out rounder and taking up more of its skull in youth. Lautenschlager also noted in the study that the shape of a T. “It seems like, really, this is an adaptation to deal with high forces during biting,” he says, “so that the skull is not in danger of deforming or being stressed too much.” Using biomechanical computer modeling, he found that these unusual shapes could have minimized the biomechanical stress on the animals’ skulls when they feasted on their prey. This appears to be convergent evolution, Lautenschlager says, where the different species independently evolved away from round eyes. For his study, published on August 11 in Communications Biology, Lautenschlager cataloged eye-socket size and shape from 410 previously documented archosaur skulls and modeled how varying sockets would affect the stresses that eating put on those skulls.īeyond just dinosaurs, other large archosaur predators during the same era also had unusual socket shapes. These can range from cavities that look like keyholes to compressed circles to wedge shapes, which all fit smaller eyes than could same-sized round sockets. Unlike modern animals’ round eye sockets, in large carnivorous dinosaurs, “we see all these strange eye socket orbital shapes,” Lautenschlager says. Skulls of different dinosaurs showing variation in eye socket shape ( stippled outline) Credit: Dr Stephan Lautenschlager, University of Birmingham “This is probably not efficient, even though it might increase the vision acuity,” Lautenschlager adds. Such large eyes could potentially consume up to 15 percent of the animal’s metabolic energy, meaning it would have to eat more just to maintain its huge eyeballs. rex’s eyes took up 20 percent of its skull in the same way some smaller dinosaurs’ eyes do, “we would have a massive eyeball 30 centimeters in diameter and 20 kilograms heavy,” Lautenschlager says. These proportions likely evolved because of its skull size: if one of a T. rex’s skull cavities would have accommodated eyes about the size of oranges in its meter-long head. A fossilized skull’s eye socket gives scientists a good idea of eye size. Such skulls can reveal a lot about an animal. Paleobiologist Stephan Lautenschlager of the University of Birmingham in England discovered this connection while digging through skull measurements of hundreds of extinct archosaurs-the taxonomic group that includes birds, crocodiles and all of their ancestors. A new study suggests that those squinty eyes could be a trade-off for powerful chomping jaws. But the seven-metric-ton predator, which hunted through the end of the Cretaceous period 65 million years ago, was not the only beast with these features: other large predatory dinosaurs also gazed through small eyes in their large head. It was an unlucky dinosaur that came face-to-face with the beady-eyed glare and giant, toothy grimace of the iconic Tyrannosaurus rex.
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