Scientists from the University of Calgary have discovered a new mid-sized dinosaur species named Khankhuuluu mongoliensis, which appears to be the 'missing link' in the evolution of tyrannosaurs, according to CBS News. This slender predatory dinosaur represents the closest known ancestor to the feared tyrannosaurs, bridging the gap between smaller forms and larger apex predators.
Named Khankhuuluu mongoliensis, meaning 'Dragon Prince' in Mongolian, the species name 'mongoliensis' refers to the place of discovery—the Gobi Desert in Mongolia. The skeleton was discovered over 50 years ago in the 1970s but, after being misidentified, the bones became part of a museum collection and were relatively untouched for almost half a century.
The significance of the specimen wasn't recognized until Darla Zelenitsky, a paleontologist at the University of Calgary, sent graduate student Jared Voris to Mongolia on a research trip, where he examined the fossil. Voris noticed frequent references to the specimens and, upon closer examination, realized they could be something special.
"I think it could be a new species," Jared Voris texted to Darla Zelenitsky from Mongolia, prompting further investigation, according to CBS News. "I said, great going, keep looking at this so we can be sure this is a new species," Zelenitsky said, but later added, "This is good, but we don't want to jump the gun on this."
"After being reexamined, Jared Voris realized the specimens were something completely different than anything ever seen before," according to Live Science. The discovery of Khankhuuluu mongoliensis has led to a revision of the tyrannosaur family tree, providing new insights into the evolution and spread of these dinosaurs, and helping clarify Tyrannosaurus rex's complicated family history.
"It's the missing link between smaller tyrannosauroids and the large predatory tyrannosaurs," Zelenitsky said, according to CBC News. Khankhuuluu mongoliensis lived approximately 86 million years ago during the Cretaceous Period and looked much like a tyrannosaur, offering a new perspective for understanding the tyrannosaur family tree.
Khankhuuluu mongoliensis was about 13 feet (4 meters) long and weighed about 1,600 pounds (750 kg), smaller than its famous descendant, Tyrannosaurus rex, which could reach 41 feet (12.5 meters) in length and weigh up to about 23,000 pounds (10,400 kilograms). "This missing link was around 750 kilograms. Its ancestors were a couple of hundred kilograms and just tiny, but then when you get to tyrannosaurs proper, they were over a thousand kilograms, up to estimates of 5,000 kilograms," Zelenitsky explained.
The research team found that Khankhuuluu mongoliensis shared many anatomical traits with tyrannosaurs but lacked certain defining characteristics, indicating it was a predecessor and not a true member of the tyrannosaur lineage. The skull of Khankhuuluu mongoliensis was more graceful and differed from the massive, deep skull of Tyrannosaurus rex, suggesting differences in diet and predatory behavior.
The discovery has shed light on the evolutionary history of tyrannosaurs, particularly the role of migration events between Asia and North America. "They show that a few big migration events back and forth between Asia and North America were the drivers of much of tyrannosaur evolution," Zelenitsky said, enriching our knowledge about dinosaurs.
Around 85 million years ago, smaller tyrannosauroid species in Asia migrated to North America, giving rise to larger tyrannosaurs through multiple migrations between the continents. The identification of Khankhuuluu mongoliensis as an ancestor and close relative of dinosaur groups provides examples of how living beings evolve over time.
"This discovery forced us to look at the family tree of tyrannosaurs in a very different light. It ended up with us rewriting the family history of tyrannosaurs," Zelenitsky added. The findings contribute to a clearer view of the evolution of tyrannosaurs and their interaction with the surrounding environment.
The researchers compared 12 species of tyrannosaurs to figure out when and where they lived, how they were related, and when any migrations might have taken place. The study has been published in the journal Nature.
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