A recently discovered dinosaur species was a small relative of Tyrannosaurus rex and has thrown light on how the reptiles came to dominate the former North American food chain.
Intrepidus Morbus named, it is believed that the species had lived 96 million years ago in what is now in Utah.
According to that, Utah was a lush delta, and Moros was, while the animal that the T-Rex was not already a terrible predator, was a paper published in the Communication Biology magazine.
Tyrannosaurus dinosaurs were the most powerful animals on the planet for 15 million years.
They could bite with enough power to sweep a bone, they had a stereoscopic vision, and they can grow rapidly to a huge amount.
"But it was not always so," said Dr Lindsay Zanno, paleontology at North Carolina State University, and head of paleontology at the North Carolina Museum of Sciences.
"Early in their turn, tyrannosaurs were healed in the shadows of archaeological strings such as those who had already set up at the top of the food chain," said the research leader.
Moros was covered by a much larger dinosaur called the Siats meekerorum.
"In short, the story of Moros and Siats is similar to the evolving David and Goliath where small tyrannosaurs survive through dramatic changes in the landscape, by raising mountains and rising sea level, while the giant of Siats and relatives disappears from existence, "North Carolina Terry Gates, paleontologist of the State University said.
"In fact ironic, once the great predators were out of the road, the small tyrannosaurs, characterized by Moros, became the largest predators in North America," he added.
Although medium tyrannosaurs have been found in North America from periods as early as Jurassic (about 150 million years ago), a little between that and 81 million years ago when large T-Rex fossils come.
"When and how fast are tyrannosaurs going from wall flowers to the king of the prom, it has been tired palaontologists for a long time," said Dr Zanno.
"The only way to attack this problem was to go out and find more data on these rare animals."
After a decade of hard search and analysis for dinosaur fossils within rocks, Dr. Zanno finally found what he was looking for – a small relative of the T-Rex, standing only three or four feet high in the hip.
Despite its detrimental size – in terms of its larger relationship – the dinosaur was the name "harbinger of doom" because he stated that the advent of the T-Rex was still a terrible predator.
"Moros was lightweight and extremely fast," said Dr Zanno.
"It could be easy to prey, while avoiding conflicts with the predators of the day.
"Although the earliest Cretaceous tyrannosaurs were small, their skeletal ads meant that they were exhausted to take advantage of new opportunities in warming up temperatures, rising sea level and varying the shrinkage of restructuring ecosystems at the beginning of the Late Cretaceous.
"We now know that it has taken less than 15 million years to get into force."