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.
Say hi to Moros, a little, human-sized, newly discovered tyrannosaur. It helps to fill in an important 70-million-year gap in the origin story of the most famous dinosaurs of all. https://t.co/wduHneenN4— Ed Yong (@edyong209) February 21, 2019
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.
“Moros was lightweight and exceptionally fast,” study lead author Lindsay Zanno told CNN.
“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.”
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.
“We now know it took them less than 15 million years to rise to power.”
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.