A newly discovered “teenaged” pachycephalosaur from the Gobi Desert in Mongolia could unlock mysteries about this fascinating group of dinosaurs. Research published on September 17 in the journal Nature reveals that this fossil is not only a new species but also the oldest and most complete skeleton of pachycephalosaurs found so far.
“Pachycephalosaurs are iconic dinosaurs, but they’re also rare and mysterious,” says Lindsay Zanno, an associate research professor at North Carolina State University and head of paleontology at the North Carolina Museum of Natural Sciences, who is the corresponding author of this study.
The specimen was found at the Khuren Dukh locality in the Eastern Gobi Basin by Tsogtbaatar Chinzorig from the Mongolian Academy of Sciences, who is the lead author of the paper and currently a research assistant at NC State.
This new species is named Zavacephale rinpoche, which combines zava, meaning “root” or “origin” in Tibetan, and cephal, meaning “head” in Latin. The specific name, “rinpoche,” translates to “precious one” in Tibetan, referring to the domed skull that was found on a cliff, resembling a dazzling jewel.
Z. rinpoche roamed the Earth roughly 108 million years ago during the Early Cretaceous period in what is now Mongolia’s Gobi Desert, an area once dotted with lakes and surrounded by cliffs. These dinosaurs were herbivores, growing up to 14 feet long (4.3 meters) and about 7 feet tall (2.1 meters), weighing between 800 and 900 pounds (363 – 410 kilograms).
“Z. rinpoche predates all known pachycephalosaur fossils by about 15 million years,” Chinzorig explains. “It was a small creature, around three feet long or less than one meter, and represents the most complete specimen found to date.”
The Z. rinpoche specimen that the team uncovered was not fully grown at the time of its death. However, it had already developed a complete dome, though it lacked the additional decorative features seen in other pachycephalosaurs.
“Z. rinpoche is crucial for understanding the development of cranial domes in pachycephalosaurs, a topic that’s been debated for years due to a lack of early forms and the fragmentary nature of most fossils in this group,” Chinzorig notes.
Determining whether two different skulls belong to distinct species or represent different growth stages of the same species is a long-standing discussion among paleontologists, and Z. rinpoche plays an important role in this debate.
“Pachycephalosaurs are known for their flashy features, but we can’t rely on those alone to determine species or growth stages since some characteristics change as they mature,” Zanno adds. “We typically estimate the age of dinosaurs by examining growth rings in their bones, but most pachycephalosaur skeletons are fragmentary. Z. rinpoche is an exceptional find because it includes limbs and a complete skull, allowing us to link growth stages and dome development like never before.”
By analyzing a thin slice of the specimen’s lower leg bone, the researchers concluded that Z. rinpoche, despite having a fully formed dome, was still a juvenile at the time of its death.
Pachycephalosaurs are famous for their large domed skulls, often imagined engaging in headbutting contests. “It’s thought that these dinosaurs used their domes for social and sexual display,” Zanno explains. “The domes probably didn’t offer any protection from predators or help with temperature regulation, so they were most likely used to impress potential mates.
“If you plan to headbutt your way into a relationship, it’s wise to start practicing early,” she jokes.
The discovery of Z. rinpoche fills significant gaps in the timeline of pachycephalosaurs, shedding light on both their existence and growth patterns.
“This specimen is a once-in-a-lifetime find. It’s remarkable for being the oldest known pachycephalosaur, pushing the fossil record back by at least 15 million years, and for its exceptional preservation,” Zanno emphasizes. “Z. rinpoche gives us an unmatched look into the anatomy and biology of pachycephalosaurs, including the structure of their hands and their use of gastroliths, or stomach stones, to aid in food digestion.”
“The newly discovered elements of Z. rinpoche, such as its hand bones, gastroliths, and an articulated tail with preserved tendons, are reshaping our understanding of their biology, movement, and overall body structure,” adds Chinzorig.
The study is published in Nature and was supported by the National Geographic Society (grant NGS-100601R-23). Contributors include Ryuji Takasaki from Okayama University of Science; Junki Yoshida from the Fukushima Museum; Batsaikhan Buyantegsh, Buuvei Mainbayar, and Khishigjav Tsogtbaatar from the Mongolian Academy of Sciences; and Ryan Tucker from Stellenbosch University.
Summary: A newly identified pachycephalosaur species, Zavacephale rinpoche, discovered in Mongolia’s Gobi Desert, is the oldest and most complete skeleton of its kind found. This “teenaged” dinosaur lived about 108 million years ago and helps illuminate the growth and evolutionary history of pachycephalosaurs, particularly their unique domed skulls, which may have played a role in social interactions rather than defense.
