The Tyrant Lizard King didn’t always hold his crown.
“They probably kept the tyrannosaurus down, they were obviously better apex predators,” says University of Calgary associate paleontology professor Darla Zelenitsky.
Meet the Ulughbegasaurus, an absolutely gargantuan theropod dinosaur that walked the earth around 90 million years ago. Zelenitsky says they were so large that the T-Rex of their time would’ve been easy prey for the species. That’s no easy feat, nor easy pill to swallow for fans of the long-reigning tyrant king.
Fellow carnivores larger than the Tyrannosaurus have come to light in the past. But this is a different scenario.
“It was like a grizzly bear compared to a coyote,” Zelenitsky adds for local Calgary Herald. Context, however, is important.
Of the fossils available, the Ulughbegasaurus’ jawbone paints the clearest picture. This was a predator that was likely 8 meters in length, or less than 30 feet. Tyrannosaurus Rex, though, was a 40-foot predator. In addition, Ulughbegasaurus would’ve weighed around 1,000 kilograms. This is over a US ton, yet a Rex was a monster of up to 9 tons. So where’s the big deal?
At the time of Ulughbegasaurus’ reign, the T-Rex had not yet evolved into an apex predator because of the Ulughbegasaurus. By the dating of their fossils, Zelenitsky and her colleagues believe this enormous theropod kept all other predatory dinosaurs at bay. It wasn’t until they perished that others, like the T-Rex, could grow to gargantuan size.
Past Dinosaur Chess Becomes Present Paleontological Puzzle
At the time of the Ulugh, T-Rex would weigh less than 200 kilograms, or 0.2 tons. That’s a whopping difference.
“The disappearance of (Ulughbegasaurus) likely allowed tyrannosaur species to become the apex predators of Asia and North America some 80 to 90 million years ago, who persisted in large forms like Albertosaurus, Gorgosaurus, and T-Rex,” adds Zelenitsky.
It’s an important discovery that helps paint a far fuller picture of the Tyrannosaurus Rex’s early days.
“The apex predator was missing from the [theropods] and now here it is,” she continues. T-Rex and their relatives would evolve during the Jurassic Period, then thrive in the Cretaceous. Both prehistoric eras are well-documented through an abundance of fossils, but the verification of the Ulughbegasaurus is like placing a glaring, long-lost piece into a wider puzzle.
And strangely, this puzzle piece has been sitting in a Russian State Geological Museum for at least three decades. It wasn’t until fellow researchers, including U of C’s paleontologists, took an interest that this discovery came to light.
Both Zelenitsky and alum Dr. Kohei Tanaka were specifically seeking a missing piece – and they found it in the Ulugh. Tanaka would make the initial identification of a unique species in 2019. His article published by the Royal Society would cement it.
“I was surprised it took so long to identify such a large predator, so this is very exciting,” Dr. Tanaka says.
In the end, the Ulughbegasaurus dinosaur would disappear around 89 million years ago, paving the way for the Tyrannosaurus Rex to claim the title of Tyrant King. The Calgary team believes this could’ve resulted from a shift in available prey or the environment itself.