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yesterday

Oldest, Most Complete Dome-Headed Dinosaur Identified as New Species From Mongolia

CT scans plus bone histology show the juvenile's dome matured early, offering a rare window into how these dinosaurs grew.

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Paleontologist Lindsay Zanno holds the fossilized skull of the Cretaceous Period dome-headed dinosaur named Zavacephale rinpoche, whose remains were found in Mongolia, at the at the Institute of Paleontology, Mongolian Academy of Sciences, in Ulaanbaatar, Mongolia, in this image released on September 17, 2025. Alessandro Chiarenza/Handout via REUTERS THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES
The fossil was discovered sticking out of the side of a cliff in Mongolia.
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Overview

  • A Nature study names the species Zavacephale rinpoche and dates it to roughly 108 million years ago, extending the pachycephalosaur record by about 14–15 million years.
  • The specimen is a near-complete juvenile that already carried a fully formed cranial dome, implying sociosexual structures developed prior to full body growth.
  • Exceptional preservation includes the first known pachycephalosaur hand bones, gastroliths, and an articulated tail with tendons, refining views of anatomy, feeding, and locomotion.
  • CT imaging of dome sutures combined with growth rings in limb bones ties developmental stage to skull architecture and indicates an early frontal-first pathway in dome evolution.
  • The fossil was recovered at the Khuren Dukh locality in Mongolia’s Eastern Gobi Basin by a Mongolian-led team working with international collaborators.