Open Paleo

Platytholus

Horner et al., 2022 plah-tee-THO-luhs

From Greek 'platys' meaning 'flat' or 'broad' and 'tholos' meaning 'dome', referring to the flattened dome on the skull of this pachycephalosaurid.

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Platytholus is an extinct genus of pachycephalosaurid dinosaur from the Late Cretaceous (Maastrichtian) Hell Creek Formation of the United States. The genus contains a single species, P. clemensi, known from a partial skull.

Diagnosis

  1. Reduced, laterally compressed tabular ornamentation along the dorsal margins of the supraorbital-postorbital
  2. Dorsolateral depression on either side of the skull where the supraorbitals meet the frontoparietal
  3. Frontoparietal dome including lateral elements trends toward rectangular in appearance dorsally
  4. Dome not strongly arched (low, broad profile)
  5. Lateral cranial elements fully incorporated into the frontoparietal without distinction, lobes absent on the lateral margins of the skull

Species

Platytholus clemensi Horner et al., 2022

Type species

Named for William A. Clemens Jr., an American paleontologist.

Holotype
MOR 2915 , Museum of the Rockies
Material
Partial skull (frontoparietal dome, posterior supraorbitals, postorbital, left squamosal).
Horizon
lower Hell Creek Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
MOR locality HC-517, Montana, United States

References

  1. Horner, J. R.; Goodwin, M. B.; Evans, D. C. (2022). A new pachycephalosaurid from the Hell Creek Formation, Garfield County, Montana, U.S.A. Journal of Vertebrate Paleontology 42(4). Informa UK Limited. doi:10.1080/02724634.2023.2190369 horner2022a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

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

    jones2026a