99-million-year-old fossil reveals new species of dog-sized dinosaur

Millions of years ago, dinosaurs ruled the Earth. But not all of them were above-ground giants; some were small and liked to spend their time in underground burrows.

Paleontologists from North Carolina State University and the North Carolina Museum of Natural Sciences have discovered a new species of dinosaur in the Cedar Mountain Formation in Utah.

This new species, called Fona herzogaeexisted 99 million years ago in Utah. In addition to this fossil, scientists have discovered several other remains of different individuals belonging to the same species in the region.

Fona “Skeletons are much more common in this area than you would expect for a small, delicate-boned animal,” said Lindsay Zanno, head of paleontology at the North Carolina Museum of Natural Sciences.

Zanno added: “The best explanation for why we find so many of them and recover them in small packs of a few individuals is that they lived at least part of the time underground. Basically, Fona did the hard work for us, digging into this whole area.”

Fona herzogae. Author: Jorge Gonzales

A herbivore the size of a dog

The well-preserved fossil, along with anatomical features, suggests that these dinosaurs likely spent part of their lives in underground burrows. This form of partially subterranean life is referred to as semifossorial.

This species is the ancestor Thescelosaurusa genus of goat-sized dinosaurs that appeared in the late Cretaceous period in North America.

The fossilized remains of Fona indicate a digging lifestyle. Strong biceps, solid muscle attachment points on the hips and legs, a fused pelvis for stability while digging, and hind limbs significantly larger than the forelimbs all suggest that Fona was well-equipped for life below the surface.

Examination of the specimen indicates that Fona was a large, dog-sized herbivore with a simpler appearance than its horned and armored cousins.

This newly described species is a distant cousin of another dinosaur that lived partly underground. Named Willo (Thescelosaurus neglectus), this dinosaur was also discovered by researchers in North Carolina.

Lisa Herzog examines Fon’s bones. Photo: NC State University

Well-preserved remains

Unlike larger dinosaurs, whose bones fossilize more easily, the complete skeletons of Fona indicate that these dinosaurs died and were buried underground, probably in their burrows.

“The fossil record favors larger animals, largely because in flooded environments like Mussentuchit, small bones at the surface often disperse, rot, or get unearthed before being buried and fossilized,” explains Haviv Avrahami, a doctoral candidate at NC State.

“But Fona is often found whole, with many bones preserved in the original death pose, chest down, forelimbs splayed, and in remarkably good condition,” Avrahami said. “If she had already been underground in a burrow before she died, this type of behavior would be more likely.”

Although paleontologists have not yet located its burrows. They have identified tunnels and chambers of its close relative, Oryctodromeus, in Idaho and Montana. This strengthens the case for Fon’s burrowing.

The discovery sheds light on a hidden aspect of life during the mid-Cretaceous, providing a more complete picture of both above-ground and underground animals.

“(Fona) enriches the fossil record and increases the known diversity of small herbivores, which are still poorly understood despite being incredibly integral components of Cretaceous ecosystems,” Avrahami concluded in a press release.


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Mrigakshi Dixit Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her professional experience spans both broadcast and digital media, giving her a taste of diverse storytelling formats. Her work has been featured in prominent publications including Nature India, Supercluster, and Astronomy magazine. If you have any ideas, feel free to reach out to her.