Open Paleo

Ajkaceratops

Ősi et al., 2010 OI-ka-SEH-ruh-tops

Named for Ajka, the town in Hungary near where it was discovered, combined with Greek 'keratops' meaning 'horned face'.

85.7–83.6 million years ago Santonian, Late Cretaceous
Late Cretaceous stages

Ajkaceratops is a genus of ceratopsian dinosaur described in 2010. It lived during the Late Cretaceous in the western Tethyan archipelago, in what is now Europe. The type species, A. kozmai, was originally described as a ceratopsian most closely related to forms in east Asia, from where its ancestors may have migrated by island-hopping. Later research, however, questioned this assignment and treated Ajkaceratops as an ornithischian of unresolved affinity. In 2026, more complete cranial remains referable to the species were described, supporting its placement as a ceratopsian.

Under dispute

Ajkaceratops kozmai is a bizarre European ornithischian of contested affinity. Its redescribers (Czepiński and Madzia, 2024) classify it only as ?Ceratopsia, noting that a ceratopsian position depends on interpreting its anterior snout element as a rostral and that it may not be a ceratopsian at all; Bertozzo and colleagues (2025) recovered it as a non-ceratopsian basal ornithopod, sister to Changmiania, only under an alternate scoring of the snout element — their main analysis retained it within Ceratopsia. Maidment and colleagues (2026), working from a much more complete referred skull, again recover it as a ceratopsian near the Ceratopsoidea.

Diagnosis

  1. Large oval accessory fenestra present between premaxilla and maxilla, with nasal excluded from its margin
  2. Part of premaxilla ventral to external naris and accessory fenestra is dorsoventrally shallow relative to its rostrocaudal length
  3. Caudolateral process of premaxilla curved along its length, becoming nearly horizontal caudally
  4. Buccal margins of predentary are sharp and not bevelled

Species

Ajkaceratops kozmai Ősi et al., 2010

Type species

Named in honor of Karoly Kozma.

Holotype
MTM V2009.192.1 , Hungarian Natural History Museum
Material
Fused premaxillae and rostral bones with fragments of the maxillae
Horizon
Csehbánya Formation, Santonian, Late Cretaceous , 85.7–83.6 million years ago
Locality
Iharkút mine, Bakony Mountains, Veszprém, Hungary

Notable specimens

  • MTM 2025.1.1

    Hungarian Natural History Museum complementary

    A referred specimen preserving a much more complete skull than the fragmentary holotype. Its cranial anatomy, described in 2026, supported placement of Ajkaceratops as a ceratopsian after earlier work had treated it as an ornithischian of uncertain affinity.

    Maidment et al. (2026)

References

  1. Ősi, A.; Butler, R. J.; Weishampel, D. B. (2010). A Late Cretaceous ceratopsian dinosaur from Europe with Asian affinities. Nature 465(7297): 466-468. Springer Science and Business Media LLC. doi:10.1038/nature09019 ősi2010a
  2. Csiki-Sava, Z.; Buffetaut, E.; Ősi, A.; Pereda-Suberbiola, X.; Brusatte, S. L. (2015). Island life in the Cretaceous — faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. ZooKeys 469: 1-161. doi:10.3897/zookeys.469.8439

    Gives a position for the Iharkút open-pit mine as a whole, which holds several bone-bearing sites.

    csiki-sava2015a
  3. Czepiński, Ł.; Madzia, D. (2024). Osteology, phylogenetic affinities, and palaeobiogeographic significance of the bizarre ornithischian dinosaur Ajkaceratops kozmai from the Late Cretaceous European archipelago. Zoological Journal of the Linnean Society 202(4): zlae048. Oxford University Press (OUP). doi:10.1093/zoolinnean/zlae048

    Redescription of Ajkaceratops; reclassified it as an ornithischian of uncertain affinity, only ?Ceratopsia, questioning the rostral interpretation on which its ceratopsian identity depends.

    czepiński2024a
  4. Maidment, S. C. R.; Butler, R. J.; Brusatte, S. L.; Meade, L. E.; Augustin, F. J.; Csiki-Sava, Z.; Ősi, A. (2026). A hidden diversity of ceratopsian dinosaurs in Late Cretaceous Europe. Nature 651(8105): 397-403. Springer Science and Business Media LLC. doi:10.1038/s41586-025-09897-w maidment2026a
  5. Bertozzo, F.; Niu, K.; Vallée Gillette, N.; Godefroit, P. (2025). Anatomical description and digital reconstruction of the skull of Jeholosaurus shangyuanensis (Dinosauria, Ornithopoda) from China. PLoS ONE 20(1): e0312519. Public Library of Science (PLoS). doi:10.1371/journal.pone.0312519

    Redescription of the Jeholosaurus skull; its main analysis kept Ajkaceratops within Ceratopsia, and only an alternate snout scoring placed it as a non-ceratopsian ornithopod sister to Changmiania.

    bertozzo2025b
  6. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the mass and hip height estimates, and the appearance features.

    jones2026a