GEOL 104 Dinosaurs: A Natural History

Fall Semester 2006
Marginocephalia: That's using your head!


  • Name means "ridge head"
  • Characterized by shelf of bone extending back over occipital region of skull
  • For a long time only known from the Cretaceous, but now Late Jurassic species are known
  • Primitive forms are bipedal; in one branch derived forms become very large and obligate quadrupeds
  • Marginocephalian skulls show a lot of suggestions of display and/or combat

    Some paleontologists have suggested that the ?Late Triassic through Late Jurassic Heterodontosauridae were more closely related to marginocephalians than to true ornithopods. If so, these would be the oldest members of this lineage.

    Except for a few fragmentary specimens, all marginocephalians known fall into one or the other of two clades: the thick-skulled Pachycephalosauria or the deep-beaked (and often frilled (and sometimes horned)) Ceratopsia.


    The other main branch of the marginocephalians are the ceratopsians: Liaoceratops, an Early Cretaceous contemporary of Psittacosaurus, is currently the oldest known member of the more advanced ceratopsian clade Neoceratopsia:

    Some neoceratopsians developed postorbital horns (one over each eye) and nasal horns. These are the Ceratopsidae. All known ceratopsids are from western North America; all are from the later part of the Late Cretaceous.

    Ceratopsids also have a shearing dental battery of teeth, with a continuous cutting surface. Coupled with their powerful jaw muscles, they probably had an extremely powerful shearing bite for dealing with tough plants.

    Ceratopsids are larger than most "protoceratopsian"-grade neoceratopsians .

    Ceratopsids are divided into two clades:

    Both ceratopsid clades contained species that lived in herds.

    Where known, juvenile centrosaurines of all species resemble each other, and only develop their autapomorphic features when nearly fully grown. (This may be true for ceratopsines, but they are not known from many juvenile specimens yet).

    Ceratopsine postorbital horns sometimes show wear or breakage halfway down their length, and there are puncture marks on some frills. Their horns may have been used for within-species combat for dominance.

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    Last modified: 14 July 2006