The discovery of remains belonging to a new species of horse-sized dinosaur is shedding light on how Tyrannosaurus Rex (T. Rex) became one of Earth's top predators, according to scientists. 
 
 The remains were unearthed in northern Uzbekistan and are now said to be providing insights into how a family of small-bodied dinosaurs evolved over millions of years to become fearsome giants. 
 
 The study shows the dinosaurs - known as tyrannosaurs - developed huge body sizes rapidly towards the end of the age of dinosaurs, and that their keen senses, which evolved earlier in much smaller species, enabled them to climb to the top of the prehistoric food chain. 
 
 Little has been known about how tyrannosaurs became the giant, intelligent predators that dominated the landscape about 66 million years ago. 
 
 A team of palaeontologists, led by researchers at the University of Edinburgh, studied a collection of tyrannosaur fossils found in the Kyzylkum desert. 
 
 Photo: Todd Marshall/University of Edinburgh/PA 
 
 Scientists said the newly-discovered species, named Timurlengia euotica, lived about 90 million years ago and the remains fill a 20-million-year gap in the fossil record of tyrannosaurs. 
 
 The species' skull was much smaller than that of T. Rex, suggesting it did not grow to the same enormous size. 
 
 But key features of Timurlengia's skull reveal its brain and senses were already highly developed, the team said. 
 
 "The ancestors of T. rex would have looked a whole lot like Timurlengia, a horse-sized hunter with a big brain and keen hearing that would put us to shame." Dr Steve Brusatte 
 
 Timurlengia was about the size of a horse and could weigh up to 250kg. It had long legs and a skull studded with sharp teeth, and was likely a fast runner, researchers added. 
 
 The first tyrannosaurs lived around 170 million years ago and were only slightly larger than a human. 
 
 But by the late Cretaceous period - around 100 million years later - tyrannosaurs had evolved into animals like T. Rex and Albertosaurus, which could weigh more than seven tonnes. 
 
 Photo: Todd Marshall/University of Edinburgh/PA 
 
 The fact the new species was still small some 80 million years after tyrannosaurs first appeared indicates that huge size developed only at the very end of the group's evolutionary history, researchers concluded. 
 
 Dr Steve Brusatte, of the University of Edinburgh's School of GeoSciences, who led the study, said: "The ancestors of T. Rex would have looked a whole lot like Timurlengia, a horse-sized hunter with a big brain and keen hearing that would put us to shame. 
 
 Photo: Steve Brusatte/University of Edinburgh/PA 
 
 "Only after these ancestral tyrannosaurs evolved their clever brains and sharp senses did they grow into the colossal sizes of T. Rex. Tyrannosaurs had to get smart before they got big." 
 
 The work was carried out in collaboration with researchers at the Russian Academy of Sciences, Saint Petersburg State University and the National Museum of Natural History, Smithsonian Institution, US. 
 
 Professor Hans Sues, of the museum, said: "Timurlengia was a nimble pursuit hunter with slender, blade-like teeth suitable for slicing through meat. 
 
 "It probably preyed on the various large plant-eaters, especially early duck-billed dinosaurs, which shared its world." 
 
 The study has been published in the journal Proceedings of the National Academy of Sciences. ||||| Todd Marshall 
 
 Brains came before brawn for tyrannosaurs. The iconic Tyrannosaurus rex, the star of Jurassic Park, emerged as a huge and cunning predator some 80 million years ago. But how it evolved has long been a mystery, because of a gap in the fossil record that began 100 million years ago. 
 
 Now, new remains that include a skull fragment show that this dinosaur started out smaller, the size of a bear, and evolved its big brain before its huge stature. 
 
 The first tyrannosaurs evolved about 170 million years ago, when they split from the group of feathered predators that later gave rise to birds. But they remained in the shadows of larger beasts, such as allosaurs and spinosaurs. They emerged as giants during a 20-million-year gap in the fossil record, when the dinosaur age was coming to an end. 
 
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 A tyrannosauroid fossil called Timurlengia euotica dating back 90 million years fills that gap, helping us understand how T. rex was able to become so big and so dominant, says Stephen Brusatte of the University of Edinburgh, UK. 
 
 The vital clues emerged two years ago when Alexander Averianov of the Russian Zoological Institute in St Petersburg showed Brusatte a braincase that was among many fossils his group had collected in the remote Bissekty formation of Uzbekistan. 
 
 “I’ve studied a lot of tyrannosaurs and a lot of braincases, and after a while I recognised it as a tyrannosaur,” Brusatte says. On further scrutiny, the team concluded it was a new species. 
 
 CT scans 
 
 CT scans revealed that Timurlengia’s brain was large for a dinosaur and that it had structures in the inner ear used for balancing and for hearing low-frequency sounds. Earlier tyrannosaurs lacked those traits, which could have helped T. rex in its niche as an apex predator. 
 
 Yet with a body mass of some 200 kilograms, Timurlengia was much smaller than T. rex, which could weigh over 5 tonnes. 
 
 The fossils support earlier proposals that T. rex evolved “head first” – brain before bulk. 
 
 But how it took over as apex predator remains unclear, although Brusatte says it may have taken advantage of the mysterious disappearance of other large predators. “It looks like the allosaurs go out and tyrannosaurs opportunistically take over,” says Brusatte. 
 
 “This is cool stuff,” says Thomas Holtz of the University of Maryland in College Park. But he notes that the remains of Timurlengia are too fragmentary to reveal other details like the length of its arms. He hopes further fossil discoveries will fill in the gaps. 
 
 The number of tyrannosaur species known has more than doubled in the past 15 years, says Mark Norell of the American Museum of Natural History in New York. “It’s a great time to be working on tyrannosaurs.” 
 
 Other Uzbek fossils collected by Averianov’s team have already yielded important insight into other dinosaurs. They include the oldest horned dinosaurs and the first duck-billed dinosaurs, both of which lived alongside T. rex, says Holtz. 
 
 Read more: Rise and fall of a dinosaur hunter; The making of T. rex 
 
 Journal reference: PNAS, DOI: 10.1073/pnas.1600140113 ||||| "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.
– Though one of the most well-known dinosaurs, Tyrannosaurus rex is actually somewhat of a mystery, having suddenly emerged as a fearsome beast some 80 million years ago. As a 20-million-year gap in the fossil record preceded T. rex, paleontologists have known little about its evolutionary path—until now. The discovery of 90-million-year-old fossils belonging to a previously unknown relative shows T. rex likely developed brains before size, reports New Scientist. Discovered in Uzbekistan in 2012, Timurlengia euotica's large brain and ears used for balancing and hearing low-frequency sounds were "almost identical to T. rex," which also shared certain bone features, researcher Stephen Brusatte tells the BBC. Yet Timurlengia was only "the size of a horse" and weighed less than 500 pounds. "Only after these ancestral tyrannosaurs evolved their clever brains and sharp senses did they grow into the colossal sizes of T. rex," weighing over five tons, Brusatte tells the Telegraph.Timurlengia was "evolving features that would eventually allow T. rex to become this super-dominant top-of-the-food-chain animal," he adds. "Tyrannosaurs had to get smart before they got big." Researchers still don't have a full picture of Timurlengia after uncovering 25 sections of its skeleton—they don't know the length of its arms, for example—but say the "nimble pursuit hunter" had long legs and was a fast runner. Timurlengia also had "slender, blade-like teeth suitable for slicing through meat" and "probably preyed on the various large plant-eaters, especially early duck-billed dinosaurs," an expert says. (One creature alive today has teeth like T. rex.)