Tyrannosaurus rex might have been the “tyrant lizard king,” but before the mighty T. rex stomped across what is now North America, it ancestors weren't exactly living like royalty: They were tiny, gangly, and quick on their feet, adapted to life in the shadows of far larger carnivores.

Now, a fossil found in Utah is helping paleontologists better understand how this region's tyrannosaurs went from ecological paupers to princes. Weighing about 170 pounds and standing less than five feet tall, the newly named species Moros intrepidus is one of the smallest dinosaurs of its kind dating back to the Cretaceous period, the time between 66 million and 145 million years ago.

At 96 million years old, Moros is also the oldest Cretaceous tyrannosaur skeleton found in this region, pushing back that particular record by 15 million years. (Get the best look yet at the face of a tyrannosaur.)

“What Moros does for us is help us understand the who, what, why, where, and when of how tyrannosaurs ascended to top predator roles on the North American continent,” says paleontologist Lindsay Zanno of the North Carolina Museum of Natural Sciences, whose team reports the fossil find today in the journal Communications Biology.

Small wonder, then, that this dinosaur has the genus name Moros: the Greek embodiment of impending doom.

Out on a limb

At the dawn of the Cretaceous, tyrannosaurs were nowhere near the titans we imagine today. Instead, they were small, scrappy predators that hunted alongside much larger meat-eating dinosaurs called allosaurs. By 80 million years ago, North America's allosaurs had faded, and tyrannosaurs had grown about 10 times larger—filling in the allosaurs' apex niche in spectacular fashion.

Dinosaurs 101 Over a thousand dinosaur species once roamed the Earth. Learn which ones were the largest and the smallest, what dinosaurs ate and how they behaved, as well as surprising facts about their extinction.

It remains a mystery, though, how North America's tyrannosaurs got big, since there's a major gap in the continent's mid-Cretaceous fossil record. With the exception of some isolated teeth, paleontologists had been missing skeletal evidence of North American tyrannosaurs from about 150 million years ago to 80 million years ago.

As a result, researchers including Zanno kept searching mid-Cretaceous rock formations. In 2013, Zanno struck gold: While walking through her field site in central Utah's Cedar Mountain Formation, she unexpectedly saw limb bones jutting out of a hillside.

“We've been hunting in this area for 10 years, and these are the only bones of this animal we've ever recovered,” she says. “It takes teams a very, very long time and and an awful lot of luck.”



Dinosaur explorer

The foot bones of Moros are so skinny, it looks ganglier than even the juveniles of later, larger tyrannosaur species. But Moros was no toddler: Close study of the bones' cross sections show that the dinosaur was at least six or seven years old when it died, making it close to adulthood.

The tiny fossil suggests that North America's tyrannosaurs stayed small until at least the time of Moros, which means that tyrannosaurs grew to movie-monster size in just 16 million years—an evolutionary sprint. Perhaps fittingly, the Moros hind limb has some of the running-adapted features seen in later, bigger tyrannosaurs. (Could you have outrun a T. rex? Here's the science.)

“Moros is important in that way; it's the first hint of tyrannosaurs that eventually became the big ones,” says Thomas Carr, a paleontologist at Carthage College and a tyrannosaur expert who wasn't involved with the study.

What's more, Moros most closely resembles tyrannosaurs that lived in Asia in the early Cretaceous. The find suggests that the ancestors of Moros crossed a land bridge from Asia into North America, as part of an exchange between the two continents that's well-documented in other dinosaur groups. To honor its journey, researchers gave Moros the globe-trotting species name of intrepidus.

Now that her team has unveiled Moros, Zanno is eager to describe its swampy home. The same rocks that once held Moros also have yielded the massive allosaur Siats and several plant-eating dinosaurs, including some that are thought to have burrowed. She is also working with researchers to study the area's fossil plant life.</s>The miniature tyrannosaur reveals when the fearsome T-rex got to grow so big.

A new species of tyrannosaur, one that was about the size of a deer, has been discovered in Utah. The new dinosaur species, which stood less than 5 feet tall, was described from a lower leg bone unearthed in the hillsides of Emery County, paleontologists announced today in a study published in Communications Biology.

Researchers first stumbled upon this unusual fossil in 2012. Since them, several more bones have emerged to complete the picture of a previously unknown tyrannosaur species — one now hailed as a diminutive relative of the fearsome Tyrannosaurus rex.

According to the Atlantic, it took a while for paleontologists to figure out that the newly uncovered bone didn’t belong to a juvenile from a large dinosaur species, but rather to an adult representing a miniature version of T-rex.

Unlike its more famous cousin, which tipped the scales at 33,000 pounds and measured a whopping 40 feet in length, the newfound species only weighed around 170 pounds and was just 6 feet long from nose to tail. At the same time, the tiny T-rex relative only stood about 3.2 feet tall at the hip – as opposed to the 15- to 20-foot-tall Tyrannosaurus rex.

The miniature tyrannosaur hailed back to a time when the “tyrant lizard king” had yet to emerge and to gain dominion over the prehistoric territory that is now North America. The newfound species lived some 96 million years ago during the Late Cretaceous – or 30 million years before the rise of Tyrannosaurus rex.

Given that the mini-tyrannosaur foreshadowed the glory of its much larger cousin, scientists have chosen to name the new species Moros intrepidus, which roughly translates as the “harbinger of doom.”

“It was a miniature harbinger of the bone-crunching tyrants to come — impending doom, indeed,” writes Ed Yong of the Atlantic.

The age and size of Moros intrepidus provided scientists with new clues on tyrannosaur evolution. For one thing, the newfound species helped narrow down the timeline of when T-rex got to grow so big.

Like many other species that flourished after the Jurassic, tyrannosaurs started out as tiny predators living in the shadow of the mighty allosaurs. Following the demise of the allosaurs in the Cretaceous, tyrannosaurs rose to power as apex predators – and they did so quite literally, increasing in mass by an exponential factor.

The discovery of Moros unveiled that, 96 million years ago, tyrannosaurs were still small-statured creatures fighting for their chance to overthrow the allosaurs. The Moros specimen unearthed in Utah was about 7-years-old at the time of death — and showed incredible predatory specialization that pointed to an excellent runner.

Since the fossil record shows that the biggest species of tyrannosaurs emerged around 80 million years ago — toward the end of the Cretaceous Period — finding Moros revealed that the terrible “tyrant lizards” only took about 15 million years to grow to their towering size.

“Although the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous,” said Zanno, who is a paleontologist at North Carolina State University.

The fantastic Moros species also helped fill in a 70-million-year gap in the fossil record. Prior to its discovery, paleontologists had found plenty of medium-sized tyrannosaur fossils from the end of the Jurassic 150 million years ago, but scarcely any Cretaceous remains predating the rise of the Tyrannosaurus rex 80 million years ago. This makes Moros intrepidus the oldest tyrannosaur from the Cretaceous period to be found in North America.</s>SALT LAKE CITY — Turns out, arid southern Utah was once a lush, prehistoric delta and the hunting grounds of a mule-deer-sized predecessor to the well-known 10-ton apex predator, Tyrannosaurus rex.

Details of the oldest Cretaceous Tyrannosaur species yet discovered in North America were published Thursday in the journal Communications Biologyby North Carolina State University paleontologist, and University of Utah graduate, Lindsay Zanno.

Moros intrepidus — "harbinger of doom" — according to Zanno's paper, is 96 million years old and helps fill in a sizeable gap in the fossil record from the 80-million-year-old giant made famous by movies like "Jurassic Park" to evidence of much earlier related species' dating back 150 million years. While scientists believe T. rex rose to become the alpha predator of the late Cretaceous period, for the 6-foot, 170-pound moros roaming Emery County back in the day, things were much different.

"With a lethal combination of bone-crunching bite forces, stereoscopic vision, rapid growth rates, and colossal size, tyrant dinosaurs reigned uncontested for 15 million years leading up to the end-Cretaceous extinction – but it wasn’t always that way,” Zanno said in a statement. “Early in their evolution, tyrannosaurs hunted in the shadows of archaic lineages such as allosaurs that were already established at the top of the food chain.”

The 70 million year gap in the fossil record for North American tyrannosaurs has left scientists scratching their heads about how the now-infamous tyrant dinosaur evolved to surpass and dominate other predators of the time. Zanno chose her Utah site specifically because of its fossil evidence from this missing era and has been working in the area for over a decade. She's also had a previous discovery from a nearby site of a giant meat-eating dinosaur called Siats meekerorum_._

Zanno said while her latest discovery was a diminutive creature for the times, it already had a combination of traits that would help propel it up the ladder of dominance.

“Moros was lightweight and exceptionally fast,” Zanno said. “These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator. It could easily have run down prey, while avoiding confrontation with the top predators of the day."

“Although the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the late Cretaceous.

“We now know it took them less than 15 million years to rise to power.”</s>Feb. 22 (UPI) -- Scientists have discovered a new tyrannosaur species, a miniature T. rex that roamed North America some 96 million years ago.

The new species, Moros intrepidus, is the oldest Cretaceous tyrannosaur yet found in North America.

The early fossil record has provided evidence of a diversity of medium-sized, primitive tyrannosaurs dating to the Jurassic period, around 150 million years ago. And 80-million-year-old Cretaceous deposits have offered plenty of fossil evidence of large tyrannosaurs.

Until now, paleontologists have learned little of the 70-million-year gap separating the two fossil-rich deposits. The newly discovered species could help scientists better understand how T. rex and its ferocious peers became apex predators.

"When and how quickly tyrannosaurs went from wallflower to prom king has been vexing paleontologists for a long time," Lindsay Zanno, paleontologist at North Carolina State University, said in a news release. "The only way to attack this problem was to get out there and find more data on these rare animals."

Zanno and her colleagues found the new fossil evidence, including teeth and a hind limb, hiding in the rocks of Utah's Upper Cedar Mountain Formation -- deposits dating to the beginning of the Late Cretaceous.

Researchers described the Moros intrepidus fossil in the journal Communications Biology.

Unlike the tyrannosaurs that came later, like T. rex, the newly discovered species was relatively small. The mini tyrannosaur was roughly the size of a modern mule deer, measuring just three to four feet tall from the hip.

Despite, Moros intrepidus's diminutive size, scientists claim the species was still a fearsome predator.

"Moros was lightweight and exceptionally fast," Zanno said. "These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator. It could easily have run down prey, while avoiding confrontation with the top predators of the day."

According to Zanno, the new species offers proof that tyrannosaurs had all the tools to become apex predators. All that was lacking was size.

"Although the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous," Zanno said. "We now know it took them less than 15 million years to rise to power."

When scientists situated Moros intrepidus on the tyrannosaur family tree, they determined the species' relatives hail from Asia. Research last year showed the land bridge connecting Siberia and Alaska served as a migrational superhighway for dinosaurs -- just as it did millions of years later for early humans.

"T. rex and its famous contemporaries such as Triceratops may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior," Zanno said. "Moros signals the establishment of the iconic Late Cretaceous ecosystems of North America."</s>The Tyrannosaurus rex may have been one of the mightiest beasts to roam the ancient Earth — though whether he was more of a scavenger than a predator has been the topic of much debate — but Rex might have never existed at all if not for his much smaller predecessors.

A newly discovered species of Tyrannosaur found in Utah is helping scientists to better understand how Tyrannosaurs arrived on the continent and spread across North America. It’s an ancestor of the Rex, but unlike its much larger successor this new species, called Moros intrepidus, wasn’t the top of its food chain.

Researchers from North Carolina State University published a new paper in Communications Biology describing the discovery and the world the new species would have lived in. Intrepidus lived in a time where larger bipedal predators like allosaurs ruled the land.

The species was traced to the late Cretaceous period, long before the age of the Rex, and a time when it would have had to contend with much larger predators and prey. Intrepidus would only have been about the size of a modern day deer, between three and four feet tall at its hip, but it was still capable of holding its own.

“Moros was lightweight and exceptionally fast,” Lindsay Zanno, lead author of the work, said in a statement. “These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator. It could easily have run down prey, while avoiding confrontation with the top predators of the day.”

Gradually, over tens of millions of years, Tyrannosaurs took the top spot, with larger and larger species that grew to dominate the ancient Earth. Exactly when and how that change took place is something that paleontologists around the world are still figuring out, but new discoveries like this one bring us a little bit closer.</s>When you think of a Tyrannosaurus Rex, you presume it was always the king of the dinosaurs.

But a newly-discovered fossil tells us that wasn't the case.

The fossil, found in Utah, is believed to be of the creature, Moros Intrepidus.

But unlike the T-Rex, which stood about 12 feet tall and weighed up to eight tons.

The Moros was between three and four feet tall.

Researchers believe Moros fills in the timeline between the earliest, smaller Tyrannosaurs and the T-Rex.

And while lightweight, the Moros was quite fast and, over millions of years, evolved into the more memorable T-Rex.

The findings were published Thursday in Communications Biology.</s>Tyrannosaurus rex wasn’t always king of the prehistoric jungle.

One hundred million years ago, carnivorous allosaurs were considered an apex predator. But how and when the theropods were replaced by tyrannosaurs remains a mystery.

A newly discovered, “diminutive” relative of the fearsome fossil helps fill a 70-million-year gap, linking early tyrannosaurs to the world-famous T. rex.

A team from the North Carolina Museum of Natural Sciences and North Carolina State University recently unearthed Moros intrepidus, a small tyrannosaur that lived about 96 million years ago in modern-day Utah.

A paper describing the oldest Cretaceous tyrannosaur species discovered in North America was published this week in the journal Communications Biology.

Medium-sized, primitive tyrannosaurs have been found in North America dating as far bas as the Jurassic (about 150 million years ago). By the Cretaceous—some 81 million years ago—the dinosaurs had grown into the enormous, iconic predators we know today.

Their growth spurt, however, was never documented; the fossil record between the two periods has long been a blank state.

“When and how quickly tyrannosaurs went from wallflower to prom king has been vexing paleontologists for a long time,” according to study co-author Lindsay Zanno, a researcher at NC State and the North Carolina Museum of Sciences. “The only way to attack this problem was to get out there and find more data on these rare animals.”

Which is exactly what she did.

A decade spent hunting for remains finally yielded teeth and a hind limb from the new old lizard. Even more telling: The lower leg bones of Moros were discovered in the same area Zanno previously found Siats meekerorum, a giant meat-eating carcharodontosaur that lived during the same period.

Tiny by comparison, Moros stands only three or four feet tall at the hip—about the size of a modern mule deer.

Zanno estimates that their Moros was more than seven years old when it died, nearly full grown.

“Although the earliest Cretaceous tyrannosaurs were small, their predatory specializations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level, and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous,” Zanno explained. “We now know it took them less than 15 million years to rise to power.”

The team also uncovered the origin of T. rex‘s lineage in North America, suggesting that its closest relatives were from Asia.
• None New Dinosaur Species With Spiny Backbone Discovered in Patagonia</s>Before Tyrannosaurus rex became the towering king of dinosaurs, its other tyrannosaur cousins were much smaller, roughly the size of a deer. The evolution of these smaller versions into T. rex is well documented in Asia, but in the North American fossil record, there’s been a 70-million-year gap in evolutionary records—until now.

Now, fossil evidence of a new tyrannosaur species closes that gap by about 15 million years. The new species is dubbed Moros intrepidus and it roamed what is now modern-day Utah about 96 million years ago, according to a new study published in Communications Biology. This pint-size T. rex predecessor—whose name is Greek for impending doom—might just help scientists understand how tyrannosaurs eventually rose to the top of the food chain in North America.

Tyrannosaurs in the late Jurassic and early Cretaceous period would have answered to a different top predator: allosaurs. When allosaurs were top dog, tyrannosaurs would have been small-to-medium sized. During this time, however, these early tyrannosaurs were developing predatory adaptations—like big, sharp teeth—that would help them easily step in as an apex predator when allosaurs disappeared by roughly 80 million years ago, according to Michael Greshko for National Geographic.

Paleontologist Lindsay Zanno of the North Carolina Museum of Natural Science and North Carolina State University and her team had been scouring the rocky deserts of Utah for over a decade when they finally found a limb bone sticking out of the ground in 2012. Over the course of a few years, they carefully retrieved the bone and several others from the earth. The samples were extremely fragmented, she says, but they were able to reassemble what appeared to be a right hind leg.

By counting growth rings in the bone, they determined the specimen was at least seven years old, ruling out the possibility that Moros could have been a juvenile of a larger tyrannosaur, reports Ed Yong at The Atlantic. The unique shape of the foot and upper leg bone helped the team determine Moros was the oldest Cretaceous-era dinosaur discovered in North America.

“What I find most interesting about what Moros can teach us about tyrannosaur evolution is that we often think about tyrannosaurs as being such incredible predators, that they were destined to rule the late Cretaceous ecosystems,” Zanno tells Smithsonian.com. “But, in fact, they were living in the shadows of these archaic dinosaur lineages when they arrived here in the North American continent. And it wasn’t until those top predators went extinct, vacating those niches in the ecosystem, that tyrannosaurs were primed and ready to take over, and they did this very quickly.”

From 80 million years ago to 150 million years ago, the tyrannosaur fossil record in North America is sparse, reports Greshko for National Geographic. There are plenty small tyrannosaur skeletons from around 150 million years ago, and then gigantic remains from 80 million years ago—but a blank slate in between, reports The Atlantic’s Yong. The discovery of 96 million-year-old Moros provides evidence that tyrannosaurs were still on the continent during the mid-Cretaceous period and that tyrannosaurs were able to evolve from the size of a horse to the size of a school bus about 16 million years.

Zanno says Moros’ long feet would have given it incredible speed, and it would have had stereoscopic vision and a highly attuned sensory system that would help its later forms dominate ecosystems. Moros differs from T. rex, though, in its size as well as its teeth.

“[Between Moros and T. rex] there were lots of intermediate [evolutionary] stages,” Hans Sues, curator of vertebrate paleontology at the National Museum of Natural History, tells Smithsonian.com. “We can see that they get bigger, that their teeth get more robust. These early tyrannosaurs have blade-like teeth, but by the time you get to T. rex, it was a predator that could crush bones so it has really massive, strong teeth that kind of look like a big banana with cutting edges.”

Sues says while he’s “surprised and excited” about the new finding, he hopes to find more complete remains of these early tyrannosaurs to better understand what they looked like and determine the timeline of specific evolutionary changes.

Zanno hopes they can eventually pinpoint exactly when allosaurs died out to help determine how tyrannosaurs made such a massive jump in size a relatively short period.

“When and where and why and how [tyrannosaurs] ascended to these top predator roles in North America has remained a mystery,” Zanno says. “We just haven’t had the fossils to answer that question. There’s still an enormous gap and discoveries that need to be made.”</s>An ancestor of the T-Rex has been discovered by scientists and the pint-sized relative is less than a third of the size of the 'tyrant king'.

Its remains were discovered in Utah and the animal lived 97 million years ago during the late Cretaceous period.

Analysis found it weighed only 180 pounds (78 kg) and was barely four foot tall at the hip - roughly the size of the modern mule deer.

It has been named Moros intrepidus, which translates to 'harbinger of doom', in recognition of its role in creating the most ferocious predator the world has ever seen when the T-Rex evolved approximately 14 million years later.

Unlike the ferocious reputation of its descendent, the dinosaur was not at the top of the pecking order and had to contend with the allosaurs - the apex predator of the time.

The discovery of the Moros intrepidus fills a 70 million year void between the existence of the earliest tyrannosaurs, approximately 150 million years ago, and when the T-Rex was first known to have existed.

It is believed to be an evolutionary mid-point which may explain how allosaurs were replaced by tyrannosaurs atop the food chain.

According to the research, published in the journal Communications Biology, the Moros intrepidus lived near the end of the allosaurs and at the evolutionary beginnings of the T-rex's reign.

This gave rise to the name, which means 'harbinger of doom.'

Researchers claim tyrannosauroids stayed small in stature for about 15 million years, before becoming behemoths like the T-Rex over another 16 million years.

Tyrannosaurus rex was one of the largest carnivores to ever live and measured around 40 feet (12 metres) in length and between 15-20 feet (4.5 metres - 6 metres) high.

Previous studies have claimed it may have weighed up to 9 tons.

But they were not always the dominant group of predators.

Dr Lindsay Zanno at North Carolina State University said: 'With a lethal combination of bone-crunching bite forces, stereoscopic vision, rapid growth rates, and colossal size, tyrant dinosaurs reigned uncontested for 15 million years leading up to the end-Cretaceous extinction - but it wasn't always that way

'Early in their evolution, tyrannosaurs hunted in the shadows of archaic lineages such as allosaurs that were already established at the top of the food chain.'

Authors wrote in the study: 'During the [late] Cretaceous, tyrannosauroids reigned supreme within terrestrial ecosystems of the Northern Hemisphere, evolving a lethal combination of colossal size, exceptional bite forces, accelerated growth rates, and adept sensory systems that would redefine top predator guilds leading up to the end-Cretaceous mass extinction event 66 million years ago.

'Yet, for the vast majority of their more than 100 million-year-long evolutionary history, tyrannosauroids were small bodied, subordinate hunters, evolving in the shadow of archaic lineages that were already established at the top of the food chain.'

The fossilised remains were found in modern day Utah when the area was a lush, deltaic environment during the Cretaceous period.

Medium-sized, primitive tyrannosaurs have been found in North America dating from the Jurassic (around 150 million years ago).

By the Cretaceous period around 81 million years ago, the North American tyrannosaurs had become the T-Rex.

Professor Zanno said: 'When and how quickly tyrannosaurs went from wallflower to prom king has been vexing paleontologists for a long time.

'The only way to attack this problem was to get out there and find more data on these rare animals.'

A decade of searching unearthed teeth and a hind limb from the new species in rocks dating back to the start of the Late Cretaceous period.

The specimen is thought to have been almost fully-grown and more than seven years old when it died.

Analysis found it stood only three or four feet tall at the hip, about the size of a modern mule deer.

'These adaptations, together with advanced sensory capabilities, are the mark of a formidable predator.

'It could easily have run down prey, while avoiding confrontation with the top predators of the day.

'Although the earliest Cretaceous tyrannosaurs were small, their predatory specialisations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the Late Cretaceous.

'We now know it took them less than 15 million years to rise to power.'

The bones of Moros also revealed the origin of T-Rex's lineage on the North American continent.

When the scientists placed Moros within the family tree of tyrannosaurs they discovered that its closest relatives were from Asia and crossed the Alaskan land bridge.

Professor Zanno said: 'T. rex and its famous contemporaries such as Triceratops may be among our most beloved cultural icons, but we owe their existence to their intrepid ancestors who migrated here from Asia at least 30 million years prior.

'Moros signals the establishment of the iconic Late Cretaceous ecosystems of North America.'</s>An NC State researcher announced the discovery of a new species of dinosaur.The new species is part of the Tyrannosaurus rex family.The fossil was found in Utah.It was identified as Moros-Intrepidus and lived approximately 96 million years ago.But, unlike the T-rex, which stood about 12 feet tall and weighed up to eight tons, the Moros was between three and four feet tall.Researchers said they believe Moros fills in the timeline between the earliest, smaller Tyrannosaurus and the T-rex.
A fossil from a new species of tyrannosaur named Moros intrepidus is discovered in the U.S. state of Utah. Scientists are using the find to better understand how Tyrannosaurus rex evolved during the Cretaceous period.