A team of international paleontologists has announced the discovery of Zavacephale rinpoche, the oldest and most complete fossil of a dome-headed pachycephalosaur dinosaur, found in Mongolia’s Early Cretaceous Khuren Dukh Formation. The study, published in Nature, provides groundbreaking insights into the origin and development of the iconic thickened skull roof—a structure long hypothesized to be used in social or sexual display.

Fig : Location map and stratigraphic position of Z. rinpoche gen. et sp. nov.

The specimen, which includes a well-preserved skull, hand bones, gastroliths, and a complete tail, represents a juvenile individual with a highly developed dome despite its small body size. Osteohistological analysis reveals that the dome matured before the rest of the skeleton—a decoupling that suggests early sociosexual maturation in these dinosaurs.

This discovery pushes back evidence of domed skulls in pachycephalosaurs by at least 14 million years and clarifies early evolutionary patterns of dome development. Phylogenetic analysis places Z. rinpoche among the earliest diverging members of the group, offering a rare glimpse into the developmental and evolutionary pathways of one of dinosaurs’ most enigmatic traits.

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Reference

Chinzorig, T., Takasaki, R., Yoshida, J. et al. A domed pachycephalosaur from the early Cretaceous of Mongolia. Nature (2025). https://doi.org/10.1038/s41586-025-09213-6