A team of scientists has identified a new member of the Tyrannosauridae family, prompting a re-evaluation of the evolutionary history of the iconic T-Rex. The discovery was made possible by the re-examination of fossils that had been misclassified and stored in a Mongolian institute for half a century.

According to Darla Zelenitsky, a paleontologist at the University of Calgary and co-author of the study published in Nature, this newly identified ancestor of the Tyrannosaurus Rex “would have been the size of a very big horse.” The dinosaur, estimated to be around four meters in length and weighing approximately 750 kg, offers valuable clues about the development of the tyrannosaurid family.

The fossils were initially unearthed in southeastern Mongolia during the early 1970s. Though, they were incorrectly classified as belonging to an Alectrosaurus, another member of the Tyrannosauridae family, at the time.

For nearly fifty years, the fossils remained in storage at the Paleontology Institute of the Academy of Sciences of Mongolia in Oulan-Bator. It wasn’t until Jared Viris, a doctoral student visiting Mongolia, noticed discrepancies that the fossils were re-evaluated, according to M^me Zelenitsky.

“It is indeed possible that other discoveries of this kind sleep in other museums,simply unrecognized,” she stated.

Unraveling the Tyrannosaurid Family tree

“It is possible that other discoveries of this kind sleep in other museums, simply unrecognized.”

In a nod to the “king” T-Rex, the new species has been named Khankhuulu Mongolieisis, meaning “the Dragon Prince of Mongolia.”

M^me Zelenitsky explained that this discovery “allowed us to clarify many elements of family history hitherto very disorderly from tyrannosauridae”, with the T-Rex being its last known member.

The T-Rex reigned as the apex predator in North America until approximately 66 million years ago, when an asteroid impact in the Gulf of Mexico led to a mass extinction event. This event wiped out three-quarters of life on Earth,including all non-avian dinosaurs.

Around 20 million years prior, Khankhuulu Mongoliensis, or a closely related species, is believed to have migrated from Asia to North America via a land bridge that connected Siberia and Alaska.

This migration is thought to have facilitated the evolution of Tyrannosauridae across the North American continent. Paleontologists hypothesize that one of these species eventually returned to Asia, leading to the emergence of two distinct subgroups.

One group consisted of smaller tyrannosaurs, weighing less than a ton and possessing elongated snouts, earning them the nickname “Pinocchio Rex.” The other group comprised gigantic species, such as the Tarbosaurus, which was only slightly smaller than the T-Rex.

Eventually, one of these large dinosaurs is believed to have migrated back to north America, ultimately evolving into the T-Rex, which dominated the region for two million years.