Fona Herzogaea recently discovered dinosaur from Utah, likely lived partly underground, evidenced by its anatomical adaptations and frequent fossil preservation in burrows, which has changed our understanding of life in the Cretaceous. Credit: Jorge Gonzalez
The discovery of the burrowing dinosaur, Fona herzogae, from the middle ofChalk period reveals a complex ecosystem with dinosaurs occupying underground niches. This underscores the diversity and ecological adaptability of dinosaurs, increasing our understanding of their role in ancient environments.
The age of the dinosaurs wasn’t just above ground. A recently discovered ancestor of Thescelosaurus reveals that these animals spent part of their time in underground burrows. This new kind contributes to our understanding of life during the Mid-Cretaceous, both above and below ground.
The new dinosaur, Fon [/Foat’NAH/] herzogae lived 99 million years ago in what is now Utah. At that time, the area was a large floodplain ecosystem sandwiched between the shores of a vast inland ocean to the east and active volcanoes and mountains to the west. It was a warm, wet, muddy environment with numerous rivers flowing through it.
Paleontologists of University of North Carolina and the North Carolina Museum of Natural Sciences excavated the fossil—and other specimens of the same species—in the Mussentuchit Member of the Cedar Mountain Formation beginning in 2013. The preservation of these fossils, along with several distinguishing features, alerted them to the possibility of digging.
Physical features and evidence of burials
Fon was a small, herbivorous dinosaur about the size of a large dog with a simple body plan. It lacks the bells and whistles typical of its highly ornamented relatives, such as horned dinosaurs, armored dinosaurs, and crested dinosaurs. But that doesn’t mean Fon was boring.
Fon shares several anatomical features with animals known for digging or burrowing, including large biceps muscles, strong muscle attachments on the hips and legs, fused bones along the pelvis—likely to aid in stability while digging—and hind limbs that are proportionately larger than its forelimbs. But that’s not the only evidence that this animal spent time underground.
3D printed Fona skull. Credit: Lindsay Zanno
“The fossil record is biased toward larger animals, largely because in floodplains like the Mussentuchit, small bones often get scattered on the surface, rotted away, or eaten before being buried and fossilized,” says Haviv Avrahami, a PhD student at NC State and a digital technician for the North Carolina Museum of Natural Sciences’ new Dueling Dinosaurs Program. Avrahami is first author of the paper describing the work.
“But Fon “It is often found complete, with many of its bones preserved in the original death pose, chest down with forelimbs spread, and in exceptionally good condition,” Avrahami says. “If it had been underground in a burrow prior to death, this type of preservation would be more likely.”
Lindsay Zanno, an associate professor at NC State, chief of paleontology at the North Carolina Museum of Natural Sciences and corresponding author on the work, agrees.
“Fon “The skeletons are much more common in this area than we would expect for a small animal with fragile bones,” Zanno says. “The best explanation for why we find so many of them, and why we find them in small bundles of multiple individuals, is that they were living underground at least part of the time. In effect, Fona did the hard work for us by burying itself all over this area.”
Although researchers have discovered the underground caves of Fonthe tunnels and the room of his closest relative, Oryctodromeushave been found in Idaho and Montana. These finds support the idea that Fon also used caves.
Fona Herzogae. Credit: Jorge Gonzalez
Cultural and scientific significance of Fona
The family name Fon comes from the ancestral creation story of the Chamorro people, the indigenous people of Guam and the Pacific Mariana Islands. Fo’na and Pontan were brother and sister explorers who discovered the island and became the land and the sky. The species name honors Lisa Herzog, the paleontology operations manager at the North Carolina Museum of Natural Sciences, for her invaluable contributions and dedication to the field of paleontology.
“I wanted to honor the indigenous mythology of Guam, where my Chamorro ancestors come from,” Avrahami says. “In the myth, Fo’na became part of the land when she died, and from her body new life sprang, which for me has to do with fossilization, beauty, and creation. Fon was probably covered in a downy layer of colorful feathers. The species name is for Lisa Herzog, who has been an integral part of all this work and one of the most exceptional Fon specimens of several individuals preserved together in what was probably a burrow.”
Fon is also a distant relative of another famous fossil from North Carolina: Willo, a Thescelosaurus neglected specimen currently held at the museum that is also thought to have adaptations for a semi-fossil — or partially subterranean — lifestyle, research published in late 2023 by Zanno and former NC State postdoctoral researcher David Button.
“T. neglect stood at the end of this line – Fon is its ancestor from about 35 million years earlier,” says Avrahami.
The researchers believe Fon is essential for increasing our understanding of Cretaceous ecosystems.
“Fon “gives us insight into the third dimension that an animal can occupy by moving underground,” Avrahami says. “It adds to the richness of the fossil record and expands the known diversity of small herbivores, which are still poorly understood despite being incredibly integral components of Cretaceous ecosystems.”
“People often have a narrow view of dinosaurs that hasn’t been caught up with by science,” Zanno says. “We now know that dinosaurs ranged in diversity from small tree-dwelling gliders and nocturnal hunters to sloth-like grazers and yes, even underground shelters.”
Reference: “A new semi-fossil thescelosaurine dinosaur from the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation, Utah” by Haviv M. Avrahami, Peter J. Makovicky, Ryan T. Tucker, and Lindsay E. Zanno, July 09, 2024, The anatomical report.
DOI: 10.1002/ar.25505