Paleontologists have unearthed fossilized remains of a previously unknown species of pachycephalosaur in the Gobi Desert, Mongolia. These fossils are the most complete and geologically oldest Pachycephalosaurus specimens discovered worldwide.
A young zavacephale rinpoche engaged in a territorial duel along the shores of a lake 108 million years ago. Image credit: Masaya Hattori.
“The Pakisepalosaurus, akin to the dome-headed dinosaurs, is one of the most intriguing dinosaurs,” states Dr. Tsogtbaatar Chinzorig, a researcher affiliated with the Mongolian Academy of Sciences and the Institute of Paleontology at North Carolina State University.
“It is thought that members of this group, characterized by their enlarged skull roofs and intricate skull features, developed a complex social structure.”
“Despite their crucial role in comprehending dinosaur behavioral ecology, the absence of uncontested early species has hindered our understanding of their origins and the reconstruction of early evolution.”
This new pachycephalosaur species has been named zavacephale rinpoche, which thrived in Mongolia during the early Cretaceous period, approximately 108 million years ago.
During this period, the region was a valley adorned with lakes and flanked by cliffs and wetlands.
“zavacephale rinpoche predates the known Pakisepalosaur fossils by about 15 million years,” Dr. Chinzorig notes.
“It was a small creature, measuring less than 1 meter (3 feet) in length, yet it stands as the most complete specimen discovered to date.”
Fossilized remains of zavacephale rinpoche were found in the Klen Duk Formation within the East Gobi Basin.
“zavacephale rinpoche represents a vital specimen for deciphering the evolution of the Pachycephalosaurus’s cranial dome. This has been a topic of debate for quite some time, given the lack of early divergent or pre-rear Cretaceous species and the fragmentary nature of most Pachyphalosaurus fossils,” Dr. Chinzorig explained.
“We’ve encountered many unique experiences worldwide,” remarked Lindsay Zanno, a researcher at North Carolina State University and director of paleontology at the North Carolina Museum of Natural Sciences.
“The domes likely provided no defense against predators or help in thermoregulation; thus, they were probably a means of display for social interactions.”
“If you seek to establish a relationship, I suggest starting your rehearsals early,” she adds.
zavacephale rinpoche fills a significant gap in the timeline of Pachycephalosaurs.
“This specimen is a unique discovery,” Dr. Zanno emphasized.
“Not only does it push the fossil record of this group back by at least 15 million years, but it is also the oldest and most well-preserved Pachycephalosaurus known, offering profound insights into its anatomy and biology, including the use of gastroliths to aid in digestion.”
“The newly recovered materials from zavacephale rinpoche are helping to reconstruct our understanding of the paleobiology, locomotion, and anatomy of these enigmatic dinosaurs, including aspects of their hands, gastroliths, and the articulated tails with preserved tendons,” Dr. Chinzorig concluded.
The findings are detailed in a study published today in the journal Nature.
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T. Chinzorig et al. A dome-shaped Pakisephalosaurus from Mongolia’s early Cretaceous period. Nature Published online on September 17th, 2025. doi:10.1038/s41586-025-09213-6
Source: www.sci.news
