When Hank Woolley cracked open a jar labeled simply “lizard,” he didn’t expect to meet a monster. Inside, stored for years in a fossil drawer at the Natural History Museum of Utah, were the scattered remains of an animal that looked—as he would later describe it—“like a goblin that sprang from the rocks.”
It was no ordinary lizard. The fossil, found two decades earlier in Utah’s Grand Staircase-Escalante National Monument, has now been identified as a new species: Bolg amondol. Though just three to four feet long—raccoon-sized, perhaps—it belonged to a group called monstersaurs, relatives of the modern-day venomous Gila monster. And like its living cousins, Bolg was likely an opportunistic predator with a taste for trouble.
“I think you’d want to avoid it,” Woolley told New Scientist.
The Goblin Prince of the Late Cretaceous
Woolley, a researcher at the Natural History Museum of Los Angeles County, named the new species in honor of Tolkien’s goblin prince, Bolg, from The Hobbit. The name’s second half—amondol—is crafted from Elvish: “amon” for mound, and “dol” for head. It’s a nod to the creature’s bony, armored skull. “Mound-headed Bolg,” as Woolley puts it, would have felt at home lurking through the undergrowth of Middle-earth.
But this real-world goblin didn’t spring from fantasy. It emerged from the Kaiparowits Formation, a 76-million-year-old slice of subtropical floodplain that today is a sunbaked stretch of Southern Utah. In the Late Cretaceous, this was a lush, humid world, buzzing with frogs, snakes, mammals, and dinosaurs. Bolg hunted them all.
“Basically anything that isn’t a plant” would have been on the menu, said Woolley, including insects, small animals, and dinosaur eggs.
The fossil itself was first spotted by paleontologist Joseph Sertich back in 2005. “[I remember seeing] a bunch of scattered bones down a low, flat, sandy area,” Sertich said. At the time, he assumed it was just another prehistoric lizard. But in 2022, he encouraged Woolley to take another look. What they found together was a game-changer.
Living Up to the Monstersaur Name
To scientists, Bolg amondol’s remains—tiny pieces of jawbone, vertebrae, hip, and armor—suggest it could shed its tail to escape predators, a behavior known as autotomy. That makes Bolg the oldest known example of this strategy among monstersaurs.
It also raises questions about how these lizards lived and evolved. Bolg’s closest known relative lived far away—in the Gobi Desert of Asia. That hints at long-forgotten migrations between continents during the Late Cretaceous, a time when land bridges allowed creatures to cross between North America and Asia.
But most of all, this discovery, published in Royal Society Open Science, adds depth to a growing realization: these ecosystems were more complex than once thought. Bolg didn’t dominate the landscape, there were plenty of other larger predators. However, it filled a key role—as a mid-sized predator in a forest teeming with dinosaurs.
“Any picture of the primeval tropical forests of North America should include nightmarish, dinosaur-hunting lizards pushing through the undergrowth and climbing through the trees,” Sertich said.
The find also points to a broader mystery—just how many large-bodied lizards were thriving during the age of dinosaurs? Most fossil lizards are found as isolated bones or teeth. Bolg’s partial skeleton is rare and unusually rich in detail.
“That means more characteristics are available for us to assess,” said Woolley. “Importantly, we can use those characteristics to understand this animal’s evolutionary relationships and test hypotheses about where it fits on the lizard tree of life.”
A Monster’s Warning for the Future
The monstersaur lineage stretches back over 100 million years. Yet its fossil record remains fragmentary.
“Bolg is a great example of the importance of natural history museum collections,” Irmis said. “It took a specialist in lizard evolution like Hank to truly recognize its scientific importance.”
Today, the landscape where Bolg once roamed is dry and stark. But its fossil-rich formations—especially in places like Grand Staircase-Escalante—continue to yield surprises. These lands, protected but not immune to political pressures, are essential to preserving such paleontological treasures.
And Bolg’s tale may carry a cautionary note as well. Randall Nydam, a lizard evolution expert not involved in the study, reflected on the monster’s fate:
“We also have to appreciate that they’re gone, and they’re gone because their environment changed.”
Just like the forests Bolg once ruled, today’s ecosystems face threats from climate shifts and human encroachment. In that sense, the goblin prince of the past might also offer a warning.
