Open Paleo

Amtocephale

Watabe et al., 2011 AM-tuh-SEF-uh-lee

Named for the Amtgai locality in Mongolia where it was found, combined with Greek 'kephale' meaning 'head'.

93.9–83.6 million years ago Turonian–Santonian, Late Cretaceous
Late Cretaceous stages

Amtocephale is a genus of pachycephalosaurid dinosaur from early Late Cretaceous (Cenomanian-Coniacian stages) deposits of southern Gobi Desert, Mongolia.

Under dispute

Amtocephale is known from a single subadult dome (Watabe and colleagues, 2011), and its subfamily placement varies between analyses. Schott and Evans (2016) recover it as the basal branch of Pachycephalosaurinae, and Evans and colleagues (2021) and Dyer and colleagues (2023) place it in an unresolved pachycephalosaurine polytomy, while Chinzorig and colleagues (2025) recover it with Stegoceras and Foraminacephale and Woodruff and colleagues (2025) leave it in a basal polytomy of Pachycephalosauridae.

Diagnosis

  1. Deep supratemporal fossae
  2. Broad (craniocaudally) prefrontal sutural surfaces with the nasal; prefrontal and anterior supraorbital sutural surfaces lying in a single plane
  3. Short parietal: parietal length to frontoparietal length ratio of 2.44 (highest ratio among known pachycephalosaurids)
  4. Posteromedial extension of the parietal sharply downturned and wide relative to the maximum width of the frontoparietal
  5. Supratemporal fenestrae absent

Species

Amtocephale gobiensis Watabe et al., 2011

Type species

Named for the Gobi Desert of Mongolia, where the fossil was discovered in the Bayanshiree Formation at the Amtgai locality.

Holotype
MPC-D 100/1203 , Paleontological Center, Mongolian Academy of Sciences
Material
Nearly complete frontoparietal dome
Horizon
Bayanshiree Formation, Turonian–Santonian, Late Cretaceous , 93.9–83.6 million years ago
Locality
Amtgai, Ömnögovi, Mongolia

References

  1. Watabe, M.; Tsogtbaatar, K.; Sullivan, R. M. (2011). A new pachycephalosaurid from the Baynshire Formation (Cenomanian-late Santonian), Gobi Desert, Mongolia. Fossil Record 3 53: 489-497. New Mexico Museum of Natural History and Science.

    Named Amtocephale and described the holotype as subadult.

    watabe2011a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate, and the appearance features.

    jones2026a
  3. Schott, R. K.; Evans, D. C. (2016). Cranial variation and systematics of Foraminacephale brevis gen. nov. and the diversity of pachycephalosaurid dinosaurs (Ornithischia: Cerapoda) in the Belly River Group of Alberta, Canada. Zoological Journal of the Linnean Society. Oxford University Press (OUP). doi:10.1111/zoj.12465

    Recovered Amtocephale as the basal branch of Pachycephalosaurinae.

    schott2016a
  4. Evans, D. C.; Brown, C. M.; You, H.; Campione, N. E. (2021). Description and revised diagnosis of Asia's first recorded pachycephalosaurid, Sinocephale bexelli gen. nov., from the Upper Cretaceous of Inner Mongolia, China. Canadian Journal of Earth Sciences 58(10): 981-992. Canadian Science Publishing. doi:10.1139/cjes-2020-0190

    Recovered Amtocephale in an unresolved pachycephalosaurine polytomy.

    evans2021a
  5. Dyer, A. D.; Powers, M. J.; Currie, P. J. (2023). Problematic putative pachycephalosaurids: synchrotron microCT imaging shines new light on the anatomy and taxonomic validity of Gravitholus albertae from the Belly River Group (Campanian) of Alberta, Canada. Vertebrate Anatomy Morphology Palaeontology 11: 1-33. University of Alberta Libraries. doi:10.18435/vamp29388

    Recovered Amtocephale in an unresolved pachycephalosaurine polytomy, and pruned it from the agreement subtree.

    dyer2023a
  6. Chinzorig, T.; Takasaki, R.; Yoshida, J.; Tucker, R. T.; Buyantegsh, B.; Mainbayar, B.; Tsogtbaatar, K.; Zanno, L. E. (2025). A domed pachycephalosaur from the early Cretaceous of Mongolia. Nature 646(8087): 1138-1145. Springer Science and Business Media LLC. doi:10.1038/s41586-025-09213-6

    Recovered Amtocephale as the sister of Stegoceras plus Foraminacephale.

    chinzorig2025a
  7. Woodruff, D. C.; Horner, J. R.; Goodwin, M. B.; Evans, D. C. (2025). The first pachycephalosaurid from the Late Cretaceous Two Medicine Formation: effects of the Western Interior Seaway on North American pachycephalosaurid evolution. Zoological Journal of the Linnean Society 205(2). Oxford University Press (OUP). doi:10.1093/zoolinnean/zlaf087

    Recovered Amtocephale in a basal polytomy of Pachycephalosauridae.

    woodruff2025a