A recent study published in the journal Nature has unveiled the discovery of a new species of early tyrannosaur, affectionately referred to as the “prince of dragons.” This remarkable species, named Khankhuuluu mongoliensis, was identified from a collection of fossils first excavated in Mongolia during the early 1970s. Scientists have determined that this species serves as an evolutionary ancestor to the well-known T. rex, or the “tyrant lizard king.”
The world of tyrannosaurs is filled with giants known for their bone-crushing bites and iconic, albeit small, arms. These large predators, scientifically classified as eutyrannosaurians, dominate the dinosaur realm. However, their origins trace back to small-bodied tyrannosauroids that roamed the Earth approximately 150 million years ago during the Jurassic period. It wasn't until the late Cretaceous period that these dinosaurs evolved into the colossal forms we often imagine. Despite their fame, their precise evolutionary origins have remained somewhat obscure, leaving a significant gap in the family tree.
Khankhuuluu is known from two partial skeletons housed at the Institute of Paleontology in Mongolia. This species, estimated to be around 86 million years old, is a critical link, representing the closest known ancestor to the later, larger tyrannosaurs like T. rex. Initially misclassified as an alectrosaurus, a lesser-known early tyrannosaur, the fossils were re-examined by a team led by University of Calgary graduate student Jared Voris. Voris made the exciting discovery during a research trip to Mongolia in 2023, suspecting that the fossils he was studying could represent a new species.
Voris's initial observation of a hollow snout bone provided a clear indication of the tyrannosaur family lineage. This discovery led to further investigations, including advanced CT scans conducted in Japan and comparative studies with alectrosaurus fossils at the American Museum of Natural History in New York. According to Darla Zelenitsky, an associate professor of paleontology at the University of Calgary, there is no doubt that Khankhuuluu is a distinct species and a direct ancestor to the apex predator tyrannosaurs.
The latest findings reveal an intermediate form of tyrannosaur — a relatively slender creature with a flat snout. Renowned paleontologist Stephen Brusatte emphasized the importance of this discovery, noting that it fills a longstanding gap in the evolutionary record, being significantly older than the famed T. rex. The discovery of Khankhuuluu contributes to a wider trend of new tyrannosaur species emerging, thanks to both fresh excavations and the re-evaluation of old fossils.
Voris and Zelenitsky's research suggests a complex narrative of species evolution and migration. It appears that Khankhuuluu and its closely related species migrated from Asia to North America around 85 million years ago, leading to the emergence of new tyrannosaur species there. Following this, several million years later, another migration back to Asia resulted in two new branches of the tyrannosaur family tree: one featuring large giants and another comprising smaller species with long, slender snouts, dubbed “Pinocchio rexes.” Ultimately, one of these giants returned to North America, leading to the evolution of T. rex.
Joseph Sertich, a vertebrate paleontologist with the Smithsonian Tropical Research Institute, likens the evolutionary patterns discovered in tyrannosaurs to those of modern big cats, where various species coexist as apex predators. The exploration of ancient connections between North America and Asia highlights a complex story of evolution, shedding light on the origins of modern ecosystems that have shared species, including humans, for the past 90 million years.
