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Post by brobear on Mar 25, 2022 5:17:39 GMT -5
Mega-Predator T. rex Had Super Senses www.amnh.org/explore/news-blogs/on-exhibit-posts/t-rex-super-senses Apart from its famously tiny arms, everything about an adult Tyrannosaurus rex was big. It weighed 6 to 9 tons and stood about 12 to 13 feet high at the hip, measuring up to 43 feet long. With foot-long teeth and a nearly 5-foot-long skull, T. rex also had the biggest bite of any known living animal—chomping down with a bite force of 7,800 pounds, or the weight of three cars. Fossil evidence shows that some of its sensory organs and processing centers were super-sized, too—giving this hunter exceptional abilities to track its prey. An adult T. rex had eyes the size of oranges—the largest of any land animal. As is common in predators, including raptors like hawks and eagles, the eyes of T. rex faced forward. They were also set wide apart, giving T. rex excellent depth perception to aid in pursuit of prey. The eyes were set relatively high on the head, boosting this dinosaur’s ability to see longer distances. And since birds and crocodiles—the closest living relatives of tyrannosaurs—can see ultraviolet light in addition to the colors seen by humans, scientists think it’s likely that T. rex could see an expanded spectrum of color. Predators with this ability could be more effective at tracking their prey through the thick camouflage of a dense forest. Analyzing a T. rex brain requires the right fossil specimens and specialized techniques. By splitting fossilized skulls, scientists have created endocasts, or models, from the hollow cavity inside the skull to determine the shape of the T. rex brain. CT scanning has also been used to make digital representations of brain cases. Looking to living animals, scientists have mapped the brains of tyrannosaurs’ closest to figure out which regions are responsible for various sensory processing and compare similar regions in the brain of T. rex. One interesting finding: T. rex brains show unusually large olfactory regions for a dinosaur, indicating the species had an exceptionally keen sense of smell.
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Post by brobear on Apr 5, 2022 3:04:14 GMT -5
T. rex's short arms may have lowered risk of bites during feeding frenzies. www.sciencedaily.com/releases/2022/04/220401094852.htm The unusually short arms of the world's fiercest predator may have shrunk to get out of the way. Extinct for 66 million years, T. rex still inspires speculation about its anatomy, behavior and fierce physique. One conundrum: its peculiarly short forelimbs, which have relatively limited mobility. While scientists have suggested explanations, a paleontologist puts the proposals to the test and finds them wanting. He hypothesizes that the arms reduced in size to limit damage, possibly fatal, when a pack of T. rexes descended on a carcass with their bone-crunching teeth. Over the two decades paleontologist Kevin Padian taught a freshman seminar called The Age of Dinosaurs, one question asked frequently by undergraduates stuck with him: Why are the arms of Tyrannosaurus rex so ridiculously short? He would usually list a range of paleontologists' proposed hypotheses -- for mating, for holding or stabbing prey, for tipping over a Triceratops -- but his students, usually staring a lifesize replica in the face, remained dubious. Padian's usual answer was, "No one knows." But he also suspected that scholars who had proposed a solution to the conundrum came at it from the wrong perspective. Rather than asking what the T. rex's short arms evolved to do, Padian said, the question should be what benefit those arms were for the whole animal. In a paper appearing in the current issue of the journal Acta Palaeontologia Polonica, Padian floats a new hypothesis: The T. rex's arms shrank in length to prevent accidental or intentional amputation when a pack of T. rexes descended on a carcass with their massive heads and bone-crushing teeth. A 45-foot-long T. rex, for example, might have had a 5-foot-long skull, but arms only 3 feet long -- the equivalent of a 6-foot human with 5-inch arms. "What if several adult tyrannosaurs converged on a carcass? You have a bunch of massive skulls, with incredibly powerful jaws and teeth, ripping and chomping down flesh and bone right next to you. What if your friend there thinks you're getting a little too close? They might warn you away by severing your arm," said Padian, distinguished emeritus professor of integrative biology at the University of California, Berkeley, and a curator at the UC Museum of Paleontology (UCMP). "So, it could be a benefit to reduce the forelimbs, since you're not using them in predation anyway." Severe bite wounds can cause infection, hemorrhaging, shock and eventual death, he said. Padian noted that the predecessors of tyrannosaurids had longer arms, so there must have been a reason that they became reduced in both size and joint mobility. This would have affected not only T. rex, which lived in North America at the end of the Cretaceous period, he said, but the African and South American abelisaurids from the mid-Cretaceous and the carcharodontosaurids, which ranged across Europe and Asia in the Early and Mid-Cretaceous periods and were even bigger than T. rex. "All of the ideas that have been put forward about this are either untested or impossible because they can't work," Padian said. "And none of the hypotheses explain why the arms would get smaller -- the best they could do is explain why they would maintain the small size. And in every case, all of the proposed functions would have been much more effective if the arms had not been reduced." He admitted that any hypothesis, including his, will be hard to substantiate 66 million years after the last T. rex became extinct.
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Post by brobear on Apr 5, 2022 3:05:00 GMT -5
Arms and the T. rex
When the great dinosaur hunter Barnum Brown discovered the first T. rex fossils in 1900, he thought the arms were too small to be part of the skeleton. His colleague, Henry Fairfield Osborn, who described and named T. rex, hypothesized that the short arms might have been "pectoral claspers" -- limbs that hold the female in place during copulation. This is analogous to some sharks and rays' pelvic claspers, which are modified fins. But Osborn provided no evidence, and Padian noted that the T. rex's arms are too short to go around another T. rex and certainly too weak to exert any control over a mate.
Over more than a century, other proposed explanations for the short arms included waving for mate attraction or social signaling, serving as an anchor to allow T. rex to get up from the ground, holding down prey, stabbing enemies, and even pushing over a sleeping Triceratops at night. Think cow-tipping, Padian said. And some paleontologists propose that the arms had no function at all, so we shouldn't be concerned with them.
Padian approached the question from a different perspective, asking what benefit shorter arms might have for the animal's survival. The answer came to him after other paleontologists unearthed evidence that some tyrannosaurids hunted in packs, not singly, as depicted in many paintings and dioramas.
"Several important quarry sites unearthed in the past 20 years preserve adult and juvenile tyrannosaurs together," he said. "We can't really assume that they lived together or even died together. We only know that they were buried together. But when you find several sites with the same animals, that's a stronger signal. And the possibility, which other researchers have already raised, is that they were hunting in groups."
Perhaps, he thought, the arms shrank to get out of the way during pack feeding. T. rex youngsters, in particular, would have been wise to wait until the larger adults were finished. In his new paper, Padian examines speculations by other paleontologists, none of which appear to have been fully tested. The first thing he determined, by measuring the lifesize T. rex cast that dominates the atrium outside the doors of the UCMP, is that none of the hypotheses would actually work.
"The arms are simply too short," he said. "They can't touch each other, they can't reach the mouth, and their mobility is so limited that they can't stretch very far, either forward or upward. The enormous head and neck are way out in front of them and pretty much form the kind of death machine you saw in 'Jurassic Park.'"
Twenty years ago, two paleontologists analyzed the arms and hypothesized that T. rex could have bench pressed about 400 pounds with its arms. "But the thing is, it can't get close enough to anything to pick it up," Padian said.
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Post by brobear on Apr 5, 2022 3:05:41 GMT -5
Beware of Komodo dragons
Padian's hypothesis has analogies in some fearsome animals today. The giant Komodo Dragon lizard (Varanus komodoensis) of Indonesia hunts in groups, and when it kills prey, the larger dragons converge on the carcass and leave the remains for the smaller ones. Maulings can occur, as they do among crocodiles during feeding. The same could be true of T. rex and other tyrannosaurids, which first appeared in the Late Jurassic and reached their peak in the Late Cretaceous before becoming extinct.
Firmly establishing the hypothesis may never be possible, Padian said, but a correlation could be found if museum specimens around the world were checked for bite marks. That would be quite a feat of fossil crowdsourcing, he admitted.
"Bite wounds on the skull and other parts of the skeleton are well known in tyrannosaurs and other carnivorous dinosaurs," he said. "If fewer bite marks were found on the reduced limbs, it could be a sign that reduction worked."
But Padian has no illusion that his idea will be the end of the story.
"What I first wanted to do was to establish that the prevailing functional ideas simply don't work," he said. "That gets us back to square one. Then, we can take an integrative approach, thinking about social organization, feeding behavior and ecological factors apart from purely mechanical considerations."
One problem in establishing the hypothesis is that there were several groups of large carnivorous dinosaurs that independently reduced their forelimbs, although in different ways.
"The sizes and proportions of the limb bones in these groups are different, but so are other aspects of their skeletons," Padian said. "We shouldn't expect them to be reduced in the same way. This is also true for the reduced wings of our large, living, flightless ratite birds, like the ostrich, the emu and the rhea. They evidently took different evolutionary paths for their own reasons."
Padian sees a common thread in the history of explanations of short arms and other characteristics of T. rex. "To me, this study of what the arms did is interesting because of how we tell stories in science and what qualifies as an explanation," he said. "We tell a lot of stories like this about possible functions of T. rex because it's an interesting problem. But are we really looking at the problem the right way?"
Padian's paper is part of a Festschift honoring mammalian paleontologist Richard Cifelli, long-time head of the Oklahoma Museum of Natural History and Presidential Professor of Biology at the University of Oklahoma in Norman.
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Post by brobear on Apr 5, 2022 3:45:26 GMT -5
( IMO ) - Flaws of Jurassic Park's T-rex: 1- Jurassic Park (1993) actually produced what is in my opinion a very realistic T-rex. However, Tyrannosaurus rex could see you clearly even if you are not moving. His vision may possibly be equal if not superior to the vision of hawks and eagles. Also note, even if he can't see you, his sense of smell was as awesome as his vision. 2- Did T-rex have feathers? Answer: possibly but unknown. T-rex was not a fast runner and would not have given the jeep much of a chase. Also, I doubt that T-rex would have been wasting energy chasing after people. He would have been searching for bigger prey. 3- The Lost World: Jurassic Park (1997) brought T-rex to San Diego, California. Reality check: T-rex would be a big easy target for one cop with a high-powered rifle. A bullet that would take down an elephant would take down a T-rex. 4- Jurassic Park III (2001) shows an epic fight between T-rex and Spinosaurus. In that fight sequence, we see the neck of Spinosaurus in the most powerful jaws of any land-based animal that ever lived. The fight would have ended right there. But the Spinosaurus, in reality, was nothing like this Hollywood monster. At the time the movie was made, Spinosaurus was viewed as being a terrestrial predator. However, Hollywood purposely gave him bigger arms and bigger claws that the real Spinosaurus had. They simply wanted a new monster to replace T-rex. In reality, Spinosaurus was an aquatic predator who hunted fish and was probably very slow and clumsy on dry land. T-rex would have killed him like a lion on a sheep. Note: I could not get into the Jurassic World movies and their hybrid dinosaur creations. But, just from watching the previews, I know that they had another big predator dinosaur to fight and kill a T-rex. ( yawn ) Why? Giganotosaurus was not bigger than T-rex and I would wager heavily on T-rex in a face-off.
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Post by brobear on Apr 15, 2022 10:26:40 GMT -5
T-rex - Biggest Theropod ever discovered. Heavier than either Giganotosaurus or Spinosaurus. 1- Tyrannosaurus rex - 10,600 kg = 23,369.00 pounds. ( Tyrannosauridae ) 2- Giganotosaurus carolini - 7,860 kg = 17,328.33 pounds. ( Carcharodontosaurinae ) 3- Mapusaurus roseae - 7,400 kg = 16,314.21 pounds. ( Carcharodontosaurinae ) 4- Deinocheirus mirificus - 7,300 kg = 16,093.75 pounds. ( Deinocheiridae ) 5- Spinosaurus aegyptiacus - 7,100 kg = 15,652.82 pounds. ( Spinosauridae ) 6- Tyrannotitan chubutensis - 6,910 kg = 15,233.94 pounds. ( Carcharodontosauridae )
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Post by brobear on May 10, 2022 5:22:37 GMT -5
This is a top-notch size comparison. If T-rex lived in Africa today, I have no doubts that he would be a hunter of elephants, rhino, and hippo.
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Post by theundertaker45 on May 10, 2022 5:56:12 GMT -5
I agree, absolutely, the Rex has got every tool necessary to make a nice meal out of any extant elephant. A certain dictator of a very bad website would ban numerous people in the past for disagreeing with him; he said a modern African elephant would easily run over a Tyrannosaurus...
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Post by brobear on May 10, 2022 6:10:23 GMT -5
I agree, absolutely, the Rex has got every tool necessary to make a nice meal out of any extant elephant. A certain dictator of a very bad website would ban numerous people in the past for disagreeing with him; he said a modern African elephant would easily run over a Tyrannosaurus... Yes; very much aware of whom you speak. However, we both know that T-rex hunted and killed dinosaurs as big or bigger than a modern-day elephant, and some of them armored and better armed.
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Post by brobear on May 25, 2022 13:18:10 GMT -5
Hot-blooded T. rex and cold-blooded Stegosaurus: Chemical clues reveal dinosaur metabolisms www.sciencedaily.com/releases/2022/05/220525110846.htm There's a new method for determining whether dinosaurs were hot- or cold-blooded, using clues in their bones that indicated how much the individual animals breathed in their last hour of life. The study shows that the bird-hipped dinosaurs like T. rex and Brachiosaurus were hot-blooded, while the lizard-hipped dinosaurs like Triceratops and Stegosaurus were cold-blooded. For decades, paleontologists have debated whether dinosaurs were warm-blooded, like modern mammals and birds, or cold-blooded, like modern reptiles. Knowing whether dinosaurs were warm- or cold-blooded could give us hints about how active they were and what their everyday lives were like, but the methods to determine their warm- or cold-bloodedness -- how quickly their metabolisms could turn oxygen into energy -- were inconclusive. But in a new paper in Nature, scientists are unveiling a new method for studying dinosaurs' metabolic rates, using clues in their bones that indicated how much the individual animals breathed in their last hour of life. "This is really exciting for us as paleontologists -- the question of whether dinosaurs were warm- or cold-blooded is one of the oldest questions in paleontology, and now we think we have a consensus, that most dinosaurs were warm-blooded," says Jasmina Wiemann, the paper's lead author and a postdoctoral researcher at the California Institute of Technology. "The new proxy developed by Jasmina Wiemann allows us to directly infer metabolism in extinct organisms, something that we were only dreaming about just a few years ago. We also found different metabolic rates characterizing different groups, which was previously suggested based on other methods, but never directly tested," says Matteo Fabbri, a postdoctoral researcher at the Field Museum in Chicago and one of the study's authors. People sometimes talk about metabolism in terms of how easy it is for someone to stay in shape, but at its core, "metabolism is how effectively we convert the oxygen that we breathe into chemical energy that fuels our body," says Wiemann, who is affiliated with Yale University and the Natural History Museum of Los Angeles County. Animals with a high metabolic rate are endothermic, or warm-blooded; warm-blooded animals like birds and mammals take in lots of oxygen and have to burn a lot of calories in order to maintain their body temperature and stay active. Cold-blooded, or ectothermic, animals like reptiles breathe less and eat less. Their lifestyle is less energetically expensive than a hot-blooded animal's, but it comes at a price: cold-blooded animals are reliant on the outside world to keep their bodies at the right temperature to function (like a lizard basking in the sun), and they tend to be less active than warm-blooded creatures. With birds being warm-blooded and reptiles being cold-blooded, dinosaurs were caught in the middle of a debate. Birds are the only dinosaurs that survived the mass extinction at the end of the Cretaceous, but dinosaurs (and by extension, birds) are technically reptiles -- outside of birds, their closest living relatives are crocodiles and alligators. So would that make dinosaurs warm-blooded, or cold-blooded? Scientists have tried to glean dinosaurs' metabolic rates from chemical and osteohistological analyses of their bones. "In the past, people have looked at dinosaur bones with isotope geochemistry that basically works like a paleo-thermometer," says Wiemann -- researchers examine the minerals in a fossil and determine what temperatures those minerals would form in. "It's a really cool approach and it was really revolutionary when it came out, and it continues to provide very exciting insights into the physiology of extinct animals. But we've realized that we don't really understand yet how fossilization processes change the isotope signals that we pick up, so it is hard to unambiguously compare the data from fossils to modern animals." Another method for studying metabolism is growth rate. "If you look at a cross section of dinosaur bone tissue, you can see a series of lines, like tree rings, that correspond to years of growth," says Fabbri. "You can count the lines of growth and the space between them to see how fast the dinosaur grew. The limit relies on how you transform growth rate estimates into metabolism: growing faster or slower can have more to do with the animal's stage in life than with its metabolism, like how we grow faster when we're young and slower when we're older." The new method proposed by Wiemann, Fabbri, and their colleagues doesn't look at the minerals present in bone or how quickly the dinosaur grew. Instead, they look at one of the most basic hallmarks of metabolism: oxygen use. When animals breathe, side products form that react with proteins, sugars, and lipids, leaving behind molecular "waste." This waste is extremely stable and water-insoluble, so it's preserved during the fossilization process. It leaves behind a record of how much oxygen a dinosaur was breathing in, and thus, its metabolic rate. The researchers looked for these bits of molecular waste in dark-colored fossil femurs, because those dark colors indicate that lots of organic matter are preserved. They examined the fossils using Raman and Fourier-transform infrared spectroscopy -- "these methods work like laser microscopes, we can basically quantify the abundance of these molecular markers that tell us about the metabolic rate," says Wiemann. "It is a particularly attractive method to paleontologists, because it is non-destructive." The team analyzed the femurs of 55 different groups of animals, including dinosaurs, their flying cousins the pterosaurs, their more distant marine relatives the plesiosaurs, and modern birds, mammals, and lizards. They compared the amount of breathing-related molecular byproducts with the known metabolic rates of the living animals and used those data to infer the metabolic rates of the extinct ones. The team found that dinosaurs' metabolic rates were generally high. There are two big groups of dinosaurs, the saurischians and the ornithischians -- lizard hips and bird hips. The lizard-hipped dinosaurs, like Triceratops and Stegosaurus, had low metabolic rates comparable to those of cold-blooded modern animals. The bird-hipped dinosaurs, including theropods and the sauropods -- the two-legged, more bird-like predatory dinosaurs like Velociraptor and T. rex and the giant, long-necked herbivores like Brachiosaurus -- were warm- or even hot-blooded. The researchers were surprised to find that some of these dinosaurs weren't just warm-blooded -- they had metabolic rates comparable to modern birds, much higher than mammals. These results complement previous independent observations that hinted at such trends but could not provide direct evidence, because of the lack of a direct proxy to infer metabolism. These findings, the researchers say, can give us fundamentally new insights into what dinosaurs' lives were like. "Dinosaurs with lower metabolic rates would have been, to some extent, dependent on external temperatures," says Wiemann. "Lizards and turtles sit in the sun and bask, and we may have to consider similar 'behavioral' thermoregulation in ornithischians with exceptionally low metabolic rates. Cold-blooded dinosaurs also might have had to migrate to warmer climates during the cold season, and climate may have been a selective factor for where some of these dinosaurs could live." On the other hand, she says, the hot-blooded dinosaurs would have been more active and would have needed to eat a lot. "The hot-blooded giant sauropods were herbivores, and it would take a lot of plant matter to feed this metabolic system. They had very efficient digestive systems, and since they were so big, it probably was more of a problem for them to cool down than to heat up." Meanwhile, the theropod dinosaurs -- the group that contains birds -- developed high metabolisms even before some of their members evolved flight. "Reconstructing the biology and physiology of extinct animals is one of the hardest things to do in paleontology. This new study adds a fundamental piece of the puzzle in understanding the evolution of physiology in deep time and complements previous proxies used to investigate these questions. We can now infer body temperature through isotopes, growth strategies through osteohistology, and metabolic rates through chemical proxies," says Fabbri. In addition to giving us insights into what dinosaurs were like, this study also helps us better understand the world around us today. Dinosaurs, with the exception of birds, died out in a mass extinction 65 million years ago when an asteroid struck the Earth. "Having a high metabolic rate has generally been suggested as one of the key advantages when it comes to surviving mass extinctions and successfully radiating afterwards," says Wiemann -- some scientists have proposed that birds survived while the non-avian dinosaurs died because of the birds' increased metabolic capacity. But this study, Wiemann says, helps to show that this isn't true: many dinosaurs with bird-like, exceptional metabolic capacities went extinct. "We are living in the sixth mass extinction," says Wiemann, "so it is important for us to understand how modern and extinct animals physiologically responded to previous climate change and environmental perturbations, so that the past can inform biodiversity conservation in the present and inform our future actions."
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Post by brobear on May 26, 2022 4:05:08 GMT -5
Quote: "We are living in the sixth mass extinction," says Wiemann.
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Post by brobear on May 27, 2022 3:44:27 GMT -5
Small ‘cousins’ of T. rex may actually have been growing teenagers Fossil analyses suggest that Nanotyrannus wasn’t a diminutive kin of the more famous behemoth www.sciencenews.org/article/small-cousins-tyrannosaurus-rex-may-have-actually-been-growing-teenagers Small but fearsome dinosaurs once thought to be pygmy kin of Tyrannosaurus rex instead may have been mere juveniles of the iconic species, new analyses of fossils suggest. The finding bolsters the case that teenage tyrannosaurs had different dining habits than their bone-crushing elders, researchers report January 1 in Science Advances.
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Post by brobear on Jun 4, 2022 8:41:19 GMT -5
The Story of Scotty The T.rex - Biggest in the World 8.8 tons (metric) is equal to 9.70 tons (short)
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Post by brobear on Jun 7, 2022 0:55:15 GMT -5
Could T-rex swim?
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Post by brobear on Jun 25, 2022 16:37:28 GMT -5
Prehistoric Planet
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Post by brobear on Jun 26, 2022 11:19:03 GMT -5
T-rex ( Prehistoric Planet )
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Post by brobear on Jul 12, 2022 7:06:54 GMT -5
A new giant dinosaur gives insight into why many prehistoric meat-eaters had such tiny arms A team co-led by University of Minnesota Twin Cities researcher Peter Makovicky and Argentinean colleagues Juan Canale and Sebastian Apesteguía has discovered a new huge, meat-eating dinosaur, dubbed Meraxes gigas. The new dinosaur provides clues about the evolution and biology of dinosaurs such as the Carcharodontosaurus and Tyrannosaurus rex -- specifically, why these animals had such big skulls and tiny arms. The researchers initially discovered Meraxes in Patagonia in 2012 and have spent the last several years extracting, preparing, and analyzing the specimen. The dinosaur is part of the Carcharodontosauridae family, a group of giant carnivorous theropods that also includes Giganotosaurus, one of the largest known meat-eating dinosaurs and one of the reptilian stars of the recently released "Jurassic World: Dominion" movie.
Though not the largest among carcharodontosaurids, Meraxes was still an imposing animal measuring around 36 feet from snout to tail tip and weighing approximately 9,000 pounds. The researchers recovered the Meraxes from rocks that are around 90-95 million years old, alongside other dinosaurs including several long-necked sauropod specimens.
Meraxes is among the most complete carcharodontosaurid skeleton paleontologists have found yet in the southern hemisphere and includes nearly the entirety of the animal's skull, hips, and both left and right arms and legs.
"The neat thing is that we found the body plan is surprisingly similar to tyrannosaurs like T. rex," said Peter Makovicky, one of the principal authors of the study and a professor in the University of Minnesota N.H. Winchell School of Earth and Environmental Sciences. "But, they're not particularly closely related to T. rex. They're from very different branches of the meat-eating dinosaur family tree. So, having this new discovery allowed us to probe the question of, 'Why do these meat-eating dinosaurs get so big and have these dinky little arms?'"
"The discovery of this new carcharodontosaurid, the most complete up to now, gives us an outstanding opportunity to learn about their systematics, paleobiology, and true size like never before," said Sebastian Apesteguía, a co-author of the study and a researcher at Maimónides University in Argentina. Quote: "What we're suggesting is that there's a different take on this," Makovicky said. "We shouldn't worry so much about what the arms are being used for, because the arms are actually being reduced as a consequence of the skulls becoming massive. Whatever the arms may or may not have been used for, they're taking on a secondary function since the skull is being optimized to handle larger prey."
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Post by brobear on Jul 22, 2022 2:27:37 GMT -5
Jurassic Park III ( 2001 ), T-rex vs Spinosaurus aegyptiacus. In this fantasy movie, the goose kills the lion. Jurassic World Dominion ( 2022 ), T-rex vs Giganotosaurus carolinii. Again, just as bad as JP3. ( After JP3, I stopped watching )
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Post by brobear on Jul 27, 2022 3:37:23 GMT -5
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Post by brobear on Aug 4, 2022 2:26:37 GMT -5
Study refutes claim that T. rex was three separate species www.sciencedaily.com/releases/2022/07/220725124108.htm A new study refutes a provocative claim made earlier this year that fossils classified as the dinosaur Tyrannosaurus rex represent three separate species. The rebuttal, published today in the journal Evolutionary Biology and led by paleontologists at the American Museum of Natural History and Carthage College, finds that the earlier proposal lacks sufficient evidence to split up the iconic species. "Tyrannosaurus rex remains the one true king of the dinosaurs," said study co-author Steve Brusatte, a paleontologist at the University of Edinburgh who conducted his Ph.D. work at the Museum. "Recently, a bold theory was announced to much fanfare: what we call T. rex was actually multiple species. It is true that the fossils we have are somewhat variable in size and shape, but as we show in our new study, that variation is minor and cannot be used to neatly separate the fossils into easily defined clusters. Based on all the fossil evidence we currently have, T. rex stands alone as the single giant apex predator from the end of the Age of Dinosaurs in North America." In March 2022, authors of the controversial study, also published in Evolutionary Biology, made the case that T. rex should be reclassified as three species: the standard T. rex, the bulkier "T. imperator," and the slimmer "T. regina." The study was based on analysis of the leg bones and teeth of 38 T. rex specimens. The authors of the new study revisited the data presented in the earlier paper and also added data points from 112 species of living dinosaurs -- birds -- and from four non-avian theropod dinosaurs. They found that the multiple species argument was based on a limited comparative sample, non-comparable measurements, and improper statistical techniques.
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