Open Paleo

Albalophosaurus

Ohashi & Barrett, 2009 AL-ba-LOH-fo-SOR-us

From Latin 'albus' meaning 'white' and Greek 'lophos' meaning 'crest' and 'sauros' meaning 'lizard', referring to the snow-covered crest of Mount Hakusan near where it was found.

125.8–121.4 million years ago Barremian, Early Cretaceous
Early Cretaceous stages

Albalophosaurus is a genus of marginocephalian ornithischian dinosaur that lived in Japan during the Early Cretaceous. The type species is Albalophosaurus yamaguchiorum.

Under dispute

Albalophosaurus yamaguchiorum is a fragmentary taxon of uncertain affinity. Its describers recovered it as a basal ceratopsian but, given weak support, treated it as Cerapoda incertae sedis (Ohashi and Barrett, 2009); Han and colleagues (2012) recover it as a basal marginocephalian, and Fonseca and colleagues (2024) variously as the earliest pachycephalosaur, the sister to Marginocephalia, or the earliest ceratopsian, depending on weighting.

Diagnosis

  1. Lateral surface of the maxilla lacks a buccal emargination (buccal ridge and buccal emargination absent), in contrast to the majority of other ornithischians.
  2. Exceptionally deep, well-defined cheek recess (buccal emargination) present on the lateral surface of the dentary, bounded laterally by a thick, prominent ridge.
  3. Labial surfaces of the maxillary tooth crowns ornamented with 10-12 fine apicobasally extending striations not present in other basal ornithischians.
  4. Maxillary tooth crowns bear a strong primary ridge offset distally and prominent secondary ridges along mesial and distal margins, with areas between ridges gently concave.
  5. Dentary tooth crowns bear a primary ridge situated near the center that splits into several branches apically, each supporting a marginal denticle; numerous secondary ridges cover the remaining crown surface.

Species

Albalophosaurus yamaguchiorum Ohashi & Barrett, 2009

Type species

Named for Ichio Yamaguchi and Mikiko Yamaguchi, who discovered and prepared many fossils from the Kuwajima Formation site in Japan.

Holotype
SBEI 176 , Museum of the Shiramine Board of Education
Material
Incomplete skull including left maxilla, left lachrymal, left jugal, left and right nasals, right frontal, left palpebral, quadrate, partial prefrontal, exoccipital/opisthotic, basisphenoid, left dentary, maxillary and dentary teeth, and other indeterminate cranial fragments.
Horizon
upper Kuwajima Formation, Barremian, Early Cretaceous , 125.8–121.4 million years ago
Locality
Rein Road tunnel, Kuwajima District, Hakusan, Ishikawa, Japan

References

  1. Ohashi, T.; Barrett, P. M. (2009). A new ornithischian dinosaur from the Lower Cretaceous Kuwajima Formation of Japan. Journal of Vertebrate Paleontology 29(3): 748-757. Informa UK Limited. doi:10.1671/039.029.0306

    Named Albalophosaurus and recovered it as a basal ceratopsian, treating it as Cerapoda incertae sedis given weak support.

    ohashi2009a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length estimate.

    jones2026a
  3. Fonseca, A. O.; Reid, I. J.; Venner, A.; Duncan, R. J.; Garcia, M. S.; Müller, R. T. (2024). A comprehensive phylogenetic analysis on early ornithischian evolution. Journal of Systematic Palaeontology 22: 2346577. doi:10.1080/14772019.2024.2346577

    Comprehensive early ornithischian phylogeny recovering Albalophosaurus in variable, unstable positions.

    fonseca2024a
  4. Han, F. L.; Barrett, P. M.; Butler, R. J.; Xu, X. (2012). Postcranial anatomy of Jeholosaurus shangyuanensis (Dinosauria, Ornithischia) from the Lower Cretaceous Yixian Formation of China. Journal of Vertebrate Paleontology 32(6): 1370-1395. doi:10.1080/02724634.2012.694385

    Jeholosaurus postcranial phylogenetic analysis recovered Albalophosaurus within Ceratopsia as a basal marginocephalian

    han2012a