Scientists Identify Closest Ancestor to Tyrannosaurs in Mongolia

Paleontologists have identified a new dinosaur species, Khankhuuluu mongoliensis, which lived approximately 86 million years ago and is considered the closest-known ancestor to the giant tyrannosaurs like Tyrannosaurus rex. This medium-sized, fleet-footed predator, weighing around 750 kilograms, fills a crucial gap in the fossil record by representing a transitional evolutionary stage from smaller early tyrannosauroids to the massive apex predators of the late Cretaceous. The discovery, based on reexamination of partial skeletons found in Mongolia’s Gobi Desert, reveals that tyrannosaurs evolved through multiple migrations between Asia and North America, leading to their diversification and gigantism. Khankhuuluu, meaning "dragon prince of Mongolia," had physical traits such as small rudimentary horns and a lightly built skull, indicating it was an agile mesopredator without the bone-crushing bite of its descendants. Researchers from the University of Calgary, including Darla Zelenitsky and Jared Voris, emphasize that this find rewrites parts of the tyrannosaur family tree and provides new insight into the early evolution and biogeography of tyrannosaurids. The study was published in the journal Nature and helps clarify the ascent of tyrannosaurs from smaller predators to dominant apex carnivores.