Discovery of Khankhuuluu mongoliensis: New Insights into T. rex Evolution

In a significant paleontological breakthrough, Jared Voris, a doctoral student at the University of Calgary, has unearthed a remarkable specimen that may redefine the narrative of Tyrannosaurus rex evolution. The skull, discovered in Mongolia's Institute of Paleontology, represents a new species named Khankhuuluu mongoliensis, a potential 'missing link' in the tyrannosaur lineage. This discovery is documented in a study published in the prestigious journal Nature on March 1, 2023.

Voris, who has dedicated years to studying tyrannosaur anatomy, recognized the importance of the partial skull soon after picking it from a collection of dinosaur bones. “I’ve studied tyrannosaur anatomy for years and immediately I thought, ‘this looks like a juvenile tyrannosaur,’” Voris stated. However, upon closer inspection, he noted that the features were distinctive from any previously known tyrannosaur species.

Khankhuuluu mongoliensis, which derives its name from the Mongolian words for 'prince' and 'dragon,' predates its larger relatives, including the formidable T. rex, by several million years. As noted by Dr. Darla Zelenitsky, a professor of paleontology at the University of Calgary and one of the study's co-authors, “Khankhuuluu is like the immediate ancestor to that. It’s also sort of the missing link.” The research suggests that this species could be the precursor to the tyrannosaur group that eventually migrated from Asia to North America approximately 90 million years ago, paving the way for the dominance of large carnivorous dinosaurs.

Historically, tyrannosaurs were relatively small, weighing around a couple of hundred kilograms. In contrast, Khankhuuluu weighs approximately 750 kilograms, situating it between its smaller ancestors and the gigantic T. rex, which could weigh over nine tonnes. The study indicates that the evolutionary trajectory of these creatures involved a rapid diversification of forms, eventually leading to the evolution of the T. rex around 70 million years ago.

The two specimens that led to the identification of Khankhuuluu were originally catalogued in the early 1970s as belonging to a different branch of dinosaur predators known as Alectrosaurus. It wasn't until Voris's meticulous examination that their true identity as early tyrannosaurs was revealed. One of the critical features that distinguished Khankhuuluu was its large hollow nasal cavity, a trait that differs from the solid bone structure found in later, heavier tyrannosaurs.

Jordan Mallon, a paleobiologist at the Canadian Museum of Nature who was not involved in the study, emphasized the significance of this discovery for understanding the evolutionary journey of tyrannosaurs. “How did a small, ancestral tyrannosaur develop into the big-headed, tiny-armed behemoth that is T. rex? This new animal bears directly on the question,” he explained.

The implications of this discovery extend beyond paleontology; it offers a clearer understanding of the ecological dynamics of the late Cretaceous period, a time when these species were beginning to adapt to new environments in North America. Voris remarked on the excitement surrounding the potential to explore evolutionary connections among various biological fields, stating, “That’s more difficult to do with other fossil data.”

As Voris prepares to defend his PhD dissertation, the scientific community eagerly anticipates further exploration and research that this discovery may inspire, potentially reshaping our understanding of dinosaur evolution. The findings from this groundbreaking research not only contribute to the rich tapestry of paleontological knowledge but also highlight the ongoing discoveries awaiting in the fossil-rich regions of Mongolia, underscoring the importance of continued exploration in understanding Earth’s prehistoric past.