The T. rex's roar has struck fear into audiences from the days of King Kong to Jurassic World, but new research found that dinosaurs probably didn't sound anything like that. (Jenny Starrs/The Washington Post) 
 
 Picture, if you will, the mighty Tyrannosaurus rex. 
 
 The odds are good what you envision has been brought to you in part by “Jurassic Park,” a plastic toy or some other facet of pop culture. (Perhaps you’re a fan of stop-motion master Ray Harryhausen.) But what Hollywood won’t teach you is that T. rex may have had feathers. 
 
 After all, today’s birds are living dinosaurs. 
 
 Now listen closely to your fearsome and possibly feathered friend. If you imagine it roaring, as both Steven Spielberg and “The Valley of Gwangi” did, we are sorry to say that sound is complete fiction. The roar of “Jurassic Park”‘s CGI tyrannosaur can be traced to a sound studio rather than the fossil record. It was a witches’ brew of baby elephant cries, tiger chuffs and a gargling alligator, remixed into a cinematically terrifying but completely artificial aural blast. 
 
 Were a dinosaur to vocalize in defense of its territory — or as a mating call — it might have sounded like one of today’s birds, scientists say. In fact, a journal article published online Monday argues that the ancient reptiles made sounds closer to the coo of a pigeon or the mumble of an ostrich. Those are far cries from mammalian screams. 
 
 [Grooves in the ground may reveal a bird-like dinosaur mating dance] 
 
 According to the new research, dino sounds may be what scientists call “closed-mouth vocalizations.” Unlike the high-pitched chirps and tweets from the open beaks of songbirds, the closed-mouth sounds are low, throaty whooshes of air. A flesh sac called an esophageal pouch enables birds with proportionally large bodies — think pigeons or doves — to produce the low murmurs. 
 
 A cooing dove with its mouth closed. (Tobias Riede/Midwestern University) 
 
 The researchers figured out the common bird sound like this: First, they collected vocal data on all sorts of animals called archosaurs, which include birds and crocodiles. And, notably, the long-dead dinosaurs. Writing in the journal Evolution, scientists from universities in Texas, Arizona, Utah and Canada analyzed the noises made by many living bird and crocodilian species. 
 
 They divided the types of sounds into various groups, including the close-mouth noises. Roughly a quarter of 200 birds species analyzed emitted the bulging closed-mouth sounds. Small birds, like sparrows and finches, did not make the noise. But birds with proportionally larger body types — like doves, ostriches and the giant New Zealand cassowary — do. This, the researchers say, suggest large-bodied dinosaurs may have had similar vocal abilities. 
 
 “Looking at the distribution of closed-mouth vocalization in birds that are alive today could tell us how dinosaurs vocalized,” said study author and University of Texas biologist Chad Eliason in a statement. 
 
 [These chickens now have dinosaur legs — but that’s not as weird as you might think] 
 
 Moreover, because not all birds had the trait, the scientists say it evolved separately in different groups of animals. It appeared in 16 distinct animal lineages, including crocodiles and birds. The scientists feel confident it could have evolved in dinosaurs, too. 
 
 
 
 A model dinosaur at the recent International Tokyo Toy show. (Kazuhiro Nogikazuhiro Nogi/AFP/Getty Images) 
 
 “A cool thing about this work is the demonstration that closed-mouth behavior evolved many times,” Tobias Riede, Midwestern University physiology expert and lead author of the paper, said in a news release. “That suggests it can emerge fairly easily and be incorporated into mating displays.” 
 
 The researchers were handicapped in their study because vocal organs, made of soft tissue, do not fossilize the way dinosaur bones do. So it’s much easier to build a big scary creature than to reconstruct what it sounded like. 
 
 But there are a few other hints in addition to this study. Based on what scientists know about birds, dinosaurs likely did not have vocal cords — those tough membranes that vibrate when a lion roars or a human speaks. Instead, they had air sacs, and it is possible dinosaurs had a birdlike syrinx, too (an organ similar to our larynxes but two-pronged and lower in the chest). 
 
 [How to find the dinosaurs that hide inside modern birds] 
 
 If a non-avian dinosaur whooshed like a bird, with its throat puffed up, the scientists suggest it may have sounded like the most intimidating large-bodied birds of today: ostriches and cassowaries. 
 
 Though ostriches are imposing creatures, their hoots leave Hollywood-trained ears wanting. The ostrich mating call is a low buzz, a sound about as ferocious as the gasps from a dying vacuum cleaner. 
 
 That said, the sound-smiths behind “Jurassic Park” were able to call on the dinosaurs’ living cousins in a few tense scenes — just not for T. rex. 
 
 As designer Gary Rydstrom told Vulture in 2013, the sibilant velociraptors — specifically, the sounds emitted right before a certain clever raptor ambushes game warden Robert Muldoon — have avian influences. 
 
 “That’s a goose,” Rydstrom said to Vulture. “Birds make pretty raspy sounds, but geese are famous for being the nastiest. You’ve got to get a goose mad and then they hiss at you, and it doesn’t take much to get a goose mad because they seem to get mad at everything.” 
 
 [The most outlandish theory yet for what killed off the dinosaurs] 
 
 For creatures that so readily capture both popular imagination and scientific study, much remains unknown about dinosaurs. 
 
 The vast majority of dinosaur species have yet to be found, argued University of Pennsylvania researchers in 2006. “It’s a safe bet that a child born today could expect a very fruitful career in dinosaur paleontology,” said paleontologist Peter Dodson at the time, after he and his co-author estimated that humans had discovered only 29 percent of dinosaur genera — the taxonomic rank made of a bundle of many species. 
 
 Dino sounds are no exception to the mystery. It is safe to say dinosaurs made sounds, as American Museum of Natural History Mark Norell put it. But exact specifics — like certainty of dino whooshes, hoots or coos — died with the animals, 65 million years ago. ||||| Colors show probability of each branch being an open-mouth vocalizer (blue) or a closed-mouth vocalizer (red). Pies show the probabilities that the ancestors of birds and crocodiles, palaeognath birds, and neognath birds used closed-mouth vocalization. Tobias Riede 
 
 AUSTIN, Texas — Dinosaurs are often depicted in movies as roaring ferociously, but it is likely that some dinosaurs mumbled or cooed with closed mouths, according to a study posted online in the journal Evolution that will be published in the August print issue. 
 
 The research examines the evolution of a specialized way birds emit sound — closed-mouth vocalization. The study emerges from a new collaboration, funded by a grant from the Gordon and Betty Moore Foundation, to understand the origin and evolution of the unique vocal organ of birds and the large array of sounds it can produce. Because birds descended from dinosaurs, the research may also shed light on how dinosaurs made sound. 
 
 
 
 X-ray image of a ring dove (Streptopelia risoria) producing cooing sounds with a closed mouth. Tobias Riede 
 
 Closed-mouth vocalizations are sounds that are emitted through the skin in the neck area while the beak is kept closed. To make them, birds typically push air that drives sound production into an esophageal pouch rather than exhale through the open beak. The coos of doves are an example of this behavior. Compared with sounds emitted through an open beak, closed-mouth vocalizations are often much quieter and lower in pitch. Birds making closed-mouth vocalizations usually do so only to attract mates or defend their territory. At other times, they emit sounds through an open mouth. 
 
 To understand when and how closed-mouth vocalization evolved, researchers with The University of Texas at Austin, Midwestern University in Arizona, Memorial University of Newfoundland and the University of Utah used a statistical approach to analyze the distribution of this vocal ability among birds and other reptilian groups. In total, the researchers identified 52 out of 208 investigated bird species that use closed-mouth vocalization. 
 
 “Looking at the distribution of closed-mouth vocalization in birds that are alive today could tell us how dinosaurs vocalized,” said Chad Eliason, a postdoctoral researcher at The University of Texas Jackson School of Geosciences and the study’s co-author. “Our results show that closed-mouth vocalization has evolved at least 16 times in archosaurs, a group that includes birds, dinosaurs and crocodiles. Interestingly, only animals with a relatively large body size (about the size of a dove or larger) use closed-mouth vocalization behavior.” 
 
 Tobias Riede, a physiology professor at Midwestern University and the study’s first author, said the association with large bodies is a matter of physics. 
 
 “The inflation of an elastic cavity could present a size-dependent challenge,” Riede said. “The lung pressure required to inflate a cavity depends on the tension in the wall of the cavity, and this tension increases for smaller body sizes.” 
 
 Researchers still are not certain about how the ancestors of modern archosaurs vocalized. But the occurrence of closed-mouth vocalization across birds and crocodiles — the two surviving groups of archosaurs — indicates that closed-mouth vocalization can emerge in diverse archosaur species depending on behavioral or environmental circumstances, Riede said. 
 
 “A cool thing about this work is the demonstration that closed-mouth behavior evolved many times,” Riede said. “That suggests it can emerge fairly easily and be incorporated into mating displays.” 
 
 An ostrich inflates its neck to make closed-mouth vocalizations. Credit: Ryan Mayock 
 
 Because dinosaurs are members of the archosaur group, and many had large body sizes, it is likely that some dinosaurs made closed-mouthed vocalizations in a manner similar to birds today, perhaps during mating displays. However, at this point in time, no direct fossil evidence exists to reveal what dinosaurs sounded like. 
 
 Julia Clarke, a professor at the Jackson School of Geosciences and co-author, said the study offers clues. 
 
 “To make any kind of sense of what nonavian dinosaurs sounded like, we need to understand how living birds vocalize,” she said. “This makes for a very different Jurassic world. Not only were dinosaurs feathered, but they may have had bulging necks and made booming, closed-mouth sounds.” 
 
 Future research by this collaboration will integrate information from fossils, experimental physiology, gene expression and sound modeling to understand the sounds that extinct early avian species, and perhaps their dinosaur ancestors, produced. ||||| "The 10,000 species of birds that live today -- from hummingbirds to ostriches -- are modern dinosaurs," Brusatte said. "They are dinosaurs in the same way that humans are mammals. The classic body plan of living birds -- feathers, wings, wishbones, air sacs extending into hollow bones -- did not evolve suddenly but was gradually assembled over tens of millions of years of evolution. But, when this body plan finally came together completely, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate." "They underwent a burst of evolution early in their history, which eventually led to the 10,000 species alive today -- more than twice the number of mammals." Photos: Audubon Report Names Birds at Climate Risk 
 
 "The oldest birds, like Archaeopteryx that lived 150 million years ago in Germany, are very hard to distinguish from their closest dinosaurian relatives," Brusatte said. "Unlike living birds, they had teeth, sharp claws on their wings, and long tails." "Over the past two decades," he continued, "over 50 new species of Mesozoic birds have been discovered in northeastern China, in the same rock units as the famous 'feathered dinosaurs.' So many birds are preserved here because entire ecosystems were buried by volcanic eruptions, turning animals to stone like a dinosaur version of Pompeii." Tiny Feathered Dinosaur Found 
 
 Dromaeosaurids were "raptor dinosaurs" that include Velociraptor from "Jurassic Park" fame. These dinosaurs were pack hunters who wielded a sharp, hyper-extendable "killer claw" on their second toe. "One of the most recently discovered dromaeosaurids is Balaur, a poodle-sized terror from Romania which had not one, but two 'killer claws' on each foot." Velociraptor Inspires Fast Running Robot 
 
 "Troodontids were probably the smartest dinosaurs of all, as they had the largest brains relative to their body size of any dinosaur group," Brusatte said. "Most troodontids were small, fast-running dinosaurs that probably ate both meat and plants." Among the most recently discovered of this group are the small, feathered Anchiornis and Xiaotingia, which lived in China about 160 million years ago. "They look eerily similar to birds, so much so that some researchers think they could be primitive birds rather than troodontids with wings and feathers," Brusatte said. World's Earliest Bird Discovered 
 
 Oviraptorosaurs, were a group of small omnivores that were lightweight, lacked teeth and had tall, hollow crests on their skulls. The recently discovered Anzu -- the so-called " chicken from hell " -- came by its nickname honestly. It towered more than five feet tall, weighed more than 400 pounds, and was covered in a coat of feathers. 
 
 Alvarezsaurs were among the smallest dinosaurs of all, measuring just a few feet long and weighing less than 5 kilograms (10 pounds). "Some of them had only a single functional finger on their hand, which they probably used to prod deep into the nests of bugs, which were one of their main food sources," Brusatte said. New Dinosaur Bolsters Bird-Dino Connection 
 
 Brusatte describes therizinosaurs as "perhaps the weirdest theropods of all." "These were big, bulky, cumbersome dinosaurs that ate plants. They had fat barrel-shaped chests, stocky legs, and big claws on their arms," Brusatte said. For many years paleontologists argued about which group this dinosaur belonged to, only recently settling on theropods. This means they were fairly closely related to birds, despite their weird anatomy. Nests of Big-Clawed Dinosaurs Found in Mongolia 
 
 Ornithomimosaurs were theropods called "ostrich mimic" dinosaurs -- for a reason. "Like living ostriches, they could run fast on their long legs and used their sharp, toothless beaks to eat a varied diet of small prey, plants, and perhaps even small shrimps in the water just like living flamingos," Brusatte explained. "A recent find in Canada showed that not only were ornithomimosaurs feathered, but they also had complex feathers on their arms that would have formed something of a wing, although they couldn't fly." 
 
 "Some of the rarest theropods (two-legged carnivorous dinos) of all, compsognathids are represented by about half a dozen species," Brusatte said. "They were small, sleek meat-eaters which ate small prey like lizards." One of the more recent finds, Juravenator from Germany, is known from a nearly complete fossil. Dinosaurs That Loved the Nightlife 
 
 Paleontologists have just assembled the most comprehensive family tree of meat-eating dinosaurs. Published in the journal Current Biology, the family tree reveals how diverse carnivorous dinosaurs were and how birds eventually evolved from them. Tyrannosaurs, including Tyrannosaurus rex , are one key group on the meat-loving dino family tree. Lead author Steve Brusatte of the University of Edinburgh's School of GeoSciences told Discovery News, "The most iconic dinosaurs of all, tyrannosaurs were more than just the 13-meter-long (nearly 43 feet long), 5-ton monster predator T. rex ." "Tyrannosaurs were an ancient group that originated more than 100 million years before T. rex , and for almost all of their evolutionary history they were small carnivores not much bigger than a human in size." New T-Rex Tracks Add to Pack-Hunting Theory 
 
 Dinosaurs not only danced, but they also did so with such enthusiasm that they left behind fossilized footprints as evidence of their moves, a new paper by an international team of paleontologists reports. 
 
 Play Video Dinosaur Sex: How Did That Work? Dinosaurs ruled the planet for 130 million years, so clearly they knew how to perpetuate themselves, but scientists have not had much to go on, in terms of their exact mechanics for doing the deed. DCI 
 
 The discovery confirms prior speculation, based on dinosaur head crests and colorful feathers, that some dinosaurs engaged in mating displays that were similar to those of modern birds. The dancing dinos, according to the paper published in the journal Scientific Reports, were likely large theropods, meaning two-legged carnivorous dinosaurs. 
 
 “They were evidently very active and perhaps driven into frenzies by the excitement of the breeding season,” project leader Martin Lockley of the University of Colorado Denver, told Discovery News. 
 
 “This is typical of some bird species,” he continued. “The extensive scrape evidence suggests much high-energy activity. If small birds get excited when breeding, imagine what big theropods might have done!” 
 
 Lockley and his team found the fossilized dinosaur scrape marks in 100-million-year-old Dakota sandstone in western Colorado. Since the footprints could not be removed from the rocks without causing damage, the scientists recreated them in virtual 3-D, using a technique of layering photographs known as photogrammetry. Rubber molds and fiberglass copies of the footprints were also made and are now stored at the Denver Museum of Nature & Science. 
 
 Various interpretations of the fossilized footprints were considered, such as whether or not dinosaurs made them while digging for food or marking territory. These were all discounted for multiple reasons, with only mating dance behavior providing the best explanation for the ancient prints. In fact, the marks closely match those created by dancing birds today, such as Atlantic puffins and ostriches. 
 
 The time and location of the prints indicate that they were made by Acrocanthosaurus, a dinosaur that grew close to 38 feet in length and weighed up to 6.8 short tons. Its rhythmic stomps and scratches, comprising what the researchers call a "scrape ceremony," must have reverberated for quite a distance. The dinosaur probably vocalized as it performed the ritualistic scraping and bobbing movements, as today’s birds do.
– Dinosaurs may have been much more like modern birds than we knew—and not just because some had feathers. A new study suggests that mighty dinosaurs of yore didn't roar, contrary to every dinosaur movie you've ever seen. Instead, they made a decidedly less scary sound called a "closed-mouth vocalization." Think of a dove cooing or perhaps an ostrich doing this grunting thing. As the scientists explain in the journal Evolution, per UT News, the sound actually comes out of the neck area after air is pushed through an esophageal pouch. In fact, the animal's mouth is shut the whole time. Lots of birds do this today, and because birds descended from dinosaurs, scientists suspect they may have communicated in a similar way. The fossil record can't prove it, though the Washington Post notes that previous research meshes with the idea, including the belief that dinosaurs had air sacs instead of vocal chords. “A cool thing about this work is the demonstration that closed-mouth behavior evolved many times,” says the lead author. “That suggests it can emerge fairly easily and be incorporated into mating displays" among different types of animals. A co-author says the study gives the impression of "a very different Jurassic world. Not only were dinosaurs feathered, but they may have had bulging necks and made booming, closed-mouth sounds." But if so, the makers of Jurassic Park didn't get it all wrong: The hiss of the film's velociraptors came from a goose, per Vulture. (Scientists have grown chickens with dinosaur legs.)