Open Paleo

Pachycephalosauridae

Sternberg, 1945 Type genus Pachycephalosaurus

Its genera lived 93.9–66.0 million years ago Late Cretaceous
Late Cretaceous stages

Pachycephalosauridae is a family of dome-headed ornithischian dinosaurs from the Late Cretaceous of western North America and central Asia. Its members are small bipedal, herbivorous to omnivorous animals distinguished by heavily thickened skulls formed by the fusion of the frontal and parietal bones and the closing of the supratemporal fenestrae; the skull roof may be raised into a full dome or remain flat or wedge-shaped, and is typically ringed by blunt horns and nodes on the squamosals, jugals, and postorbitals. The family spans basal, Stegoceras-grade forms with incipient or flat skull roofs through the fully domed subfamily Pachycephalosaurinae, defined as all pachycephalosaurids closer to Pachycephalosaurus than to Stegoceras (Sereno, 1998), and encompassing the more derived genera such as Prenocephale, Tylocephale, and Pachycephalosaurus. Because most specimens consist only of the durable frontoparietal dome, classification within the group relies almost entirely on cranial features, and several genera once assigned here have since been reidentified as other kinds of animals. The domes are widely interpreted as structures used in head- or flank-butting contests, an idea supported by the high frequency of healed cranial injuries found on them.

Diagnosis

  1. Thickened frontoparietal ranging from flat to fully domed
  2. Squamosal developed into a deep plate on the occiput with enlarged upper-outer corners
  3. Variably developed nodes, in rows or clusters, on the squamosal
  4. Broad squamosal exposure on the occiput
  5. Supratemporal fenestrae ranging from open to closed

Clades within Pachycephalosauridae

Genera placed directly in Pachycephalosauridae

  • Amtocephale Watabe et al., 2011 Turonian–Santonian (93.9–83.6 Ma)Mongoliaunder dispute
  • Colepiocephale Sullivan, 2003 Campanian (83.6–72.2 Ma)Canada
  • Hanssuesia Disputed Sullivan, 2003 Campanian (83.6–72.2 Ma)Canada
  • Stegoceras Lambe, 1902 Campanian (83.6–72.2 Ma)Canada
  • Texacephale Nomen dubium Longrich et al., 2010 Campanian (83.6–72.2 Ma)United Statesincertae sedis

References

  1. Sternberg, C. M. (1945). Pachycephalosauridae proposed for dome-headed dinosaurs, Stegoceras lambei, n. sp., described. Journal of Paleontology 19.

    Named the family Pachycephalosauridae.

    sternberg1945a
  2. 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

    Comprehensive systematic analysis of pachycephalosaurid diversity.

    schott2016a
  3. Sereno, P. C. (1998). A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210: 41-83. doi:10.1127/njgpa/210/1998/41

    Defined Pachycephalosaurinae as all pachycephalosaurids closer to Pachycephalosaurus than to Stegoceras.

    sereno1998a