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.”