These ‘Dragon Prince’ Fossils Spent Decades in Museum Drawers. Now, They Could Rewrite the T. Rex Family Tree
Two partial skeletons housed in a Mongolia museum were reexamined by researchers and found to represent a previously unknown species
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A newly identified species of dinosaur is helping researchers clarify the still-mysterious evolution of the fearsome Tyrannosaurus rex.
Paleontologists reexamined two partial skeletons that had been sitting in a collection at the Mongolian Academy of Sciences for decades. Although they had been previously described in the 1970s as belonging to Alectrosaurus, an early cousin of tyrannosaurs, the scientists thought there might be more to the fossils.
After taking a closer look at the bones, Jared Voris, a paleontologist at the University of Calgary in Canada, determined that their anatomy set them apart from true tyrannosaurs. “I realized it was something completely different than anything we’d ever seen,” says Voris to Chris Simms at Live Science. “And it actually represented the ancestor of all of our big apex predatory tyrannosaurs that we find both here in Alberta and in Mongolia and China.”
The findings, published in the journal Nature on Wednesday, offer insight into how several Cretaceous dinosaurs are related. “What started as the discovery of a new species ended up with us rewriting the family history of tyrannosaurs,” study co-author Darla Zelenitsky, a paleontologist at the University of Calgary, tells Ashley Strickland at CNN.
The scientists named the newly discovered species Khankhuuluu mongoliensis, based on the Mongolian words for prince and dragon. The species lived about 86 million years ago—and at 13 feet long and just 6.5 feet tall at the hip, it would have looked like a much smaller tyrannosaur.
Due to their age, the fossils help fill in a key gap in dinosaur history—a period between about 85 million and 100 million years ago, when conditions didn’t preserve many fossils. Before that time, tyrannosauroids were smaller predators, but by the end of that window, they had ballooned in size by about ten times.
“Khankhuuluu is essentially the missing link between smaller, earlier forms and these large apex predators that we’ve come to know and love, like T. rex,” Zelenitsky explains to Michael Greshko at Science.
In another part of their research, the team compared fossils from 12 tyrannosaur species and pieced together how and when they dispersed across the Earth. They uncovered three major migration events between Asia and North America. “The tyrannosaur family tree was shaped by migration, just like so many of our human families,” Steve Brusatte, a paleontologist and evolutionary biologist at the University of Edinburgh who wasn’t involved in the research, tells Live Science.
Roughly 85 million years ago, Khankhuuluu, or a species like it, crossed a land bridge from Asia into North America. Its descendants grew increasingly larger and became true tyrannosaurs, the dominant predators in North America in the late Cretaceous period.
Then, about 12 million years after that, some of these tyrannosaurs made their way back to Asia in a second migration. They gave rise to two distinct lineages of Asian tyrannosaurs: one group of giant dinosaurs and one smaller-bodied group with long, shallow snouts, known as “Pinocchio-rexes.”
Finally, in a third migration event, a species from the large tyrannosaur subgroup traveled back to North America some 68 million years ago. That lineage is likely the one that ultimately evolved into the famous T. rex.
While more fossil samples will help researchers further illuminate tyrannosaur evolution, the study also highlights the importance of revisiting old findings. “We know so much more about tyrannosaurs now,” says Thomas Carr, an associate professor of biology at Carthage College who was not involved in the study, to CNN. “A lot of these historical specimens are definitely worth their weight in gold for a second look.”
