For 20 years, the remains of a giant lizard that lived alongside dinosaurs were tucked away in a jar at the Natural History Museum of Utah. Simply labeled “lizard,” the fragmented and several millennia-old bones actually belonged to an entirely new species of giant lizard dug up from the Grand Staircase-Escalante National Monument in southern Utah in 2005.

Bolg amondol was a raccoon-sized armored mostesaurian lizard that lived about 77 million years ago, similar to today’s Gila monsters (Heloderma horridum). It is named after the goblin prince from The Hobbit by JRR Tolkien and is described in a study published June 17 in the open-access journal Royal Society Open Science. It also serves as another reminder to double check those museum cabinets.

Size comparison of the holotype specimen of Bolg amondol (UMNH VP 16266, left, Natural History Museum of Utah / Bureau of Land Management) and a modern Gila monster (Heloderma suspectum, right). Gold: preserved skeletal elements. Light gray: reconstructed elements based on preserved material. Dark gray: missing skeletal elements, based on publicly available rendered CT scans of Heloderma horridum available on morphosource.org (UF:Herp 153328). CREDIT: Dr. Hank Woolley

Meet the Monstersaurs

The living and fossil lizards in the clade Monstersauria are defined by their large size and distinctive features, including pitted, polygonal armor attached to their skulls and sharp, spire-like teeth. While these lizards have been on Earth for roughly 100 million years, their fossil record is largely incomplete. Finding this new species of Bolg was a step towards understanding more about these lizards–and Bolg would have been quite the formidable monster.

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“Three feet tip to tail, maybe even bigger than that, depending on the length of the tail and torso,” said Hank Woolley, a study co-author and paleontologist at the Natural History Museum of Los Angeles’ Dinosaur Institute who found the unsuspecting glass jar. “So by modern lizard standards, a very large animal, similar in size to a Savannah monitor lizard; something that you wouldn’t want to mess around with.”

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Finding this new species of monstersaur indicates that there were probably many more kinds of big lizards roaming the Earth during the Late Cretaceous–just before the dinosaurs went extinct.

Bolg’s closest known relative, Gobiderma pulchrum, once stalked Asia’s Gobi Desert. While paleontologists have long known that dinosaurs traveled between the once connected continents during the Late Cretaceous Period, Bolg reveals that smaller animals made similar treks. According to the team, this suggests common patterns of biogeography across land-dwelling vertebrates during this time.

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The specimens in this study were first uncovered in 2005 in the Kaiparowits Formation of Grand Staircase-Escalante National Monument. This area overseen by the United States Bureau of Land Management has emerged as a paleontological hotspot over the past 25 years, producing dozens of new species. Discoveries like this also underscore the importance of keeping public lands in the United States safe for future scientific research.

Piecing together the past

The team used tiny pieces of the skull, vertebrae, girdles, limbs, and the bony armor called osteoderms to identify this new species.

“What’s really interesting about this holotype specimen of Bolg is that it’s fragmentary, yes, but we have a broad sample of the skeleton preserved,” Woolley said. “There’s no overlapping bones—there’s not two left hip bones or anything like that. So we can be confident that these remains likely belonged to a single individual.”

Identified bones belonging to Bolg amondol (Specimen UMNH VP 16266, Natural History Museum of Utah / Bureau of Land Management). They are not much to look at, but they are jam-packed with valuable information on the anatomy and lifestyle of Bolg amondol. CREDIT: Photo by Dr. Hank Woolley.

Most of the fossil lizards that lived during the Age of Dinosaurs were even more fragmented. Only single isolated bones or teeth are left over. Even though Bolg was found in pieces, the parts of its skeleton that survived so many millions of years contain a treasure trove of information.

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“That means more characteristics are available for us to assess and compared to similar-looking lizards,” 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.”

Paleontologist and co-author Randy Irmis from the University of Utah adds, “Bolg is a great example of the importance of natural history museum collections. Although we knew the specimen was significant when it was discovered back in 2005, it took a specialist in lizard evolution like Hank to truly recognize its scientific importance, and take on the task of researching and scientifically describing this new species.”

Publicly available rendered CT scan of Heloderma horridum (UF:Herp:153328) from morphosource.org used for comparison to Bolg amondol, with mound-like, polygonal osteoderms in green (left). Skull of the modern monstersaur Heloderma horridum (LACM 159136), from the herpetology collection at NHMLAC, used for comparison with Bolg amondol (right). CREDIT: Dr. Hank Woolley

A species fit for both Middle-Earth and a ‘lost continent’

Woolley used Sindarin—the language Tolkien created for his elves—to craft the species epithet. “Amon” means “mound,” and “dol” means “head” in the Elvish language, referencing the mound-like osteoderms found on the skulls of Bolg and other monstersaurs.

“Bolg is a great sounding name. It’s a goblin prince from The Hobbit, and I think of these lizards as goblin-like, especially looking at their skulls,” Woolley said in a statement.

[ Related: Gila monster spit inspired a new way to detect rare pancreatic tumors. ]

Some of the other fossils described in the study include well-armored skull bones. This indicates that the ancient, seasonally tropical forests that once covered present day southern Utah were home to at least three species of large, predatory lizards. This land was once part of a “lost continent” called Laramidia. Laramidia formed about 99 million years ago, when an ancient shallow sea flooded central North America. The seaway split eastern and western portions of the continent for millions of years.

“Even though these lizards were large, their skeletons are quite rare, with most of their fossil record based on single bones and teeth,” said co-author Joe Sertich from the Smithsonian Tropical Research Institute and Colorado State University. “The exceptional record of big lizards from Grand Staircase-Escalante National Monument may prove to be a normal part of dinosaur-dominated ecosystems from North America, filling key roles as smaller predators hunting down eggs and small animals in the forests of Laramidia.”