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The Marginocephalia ("fringed heads") are a clade of extinct herbivorous dinosaurs that inherited a slight shelf or frill at the back of their skull from their common ancestor back in the Early/mid Cretaceous period. This "margin" was elaborated differently in the two main subgroups of the Marginocephalia. You are probably familiar with some of these taxa — they include the "bone-headed" pachycephalosaurs (below left) and the frilled Ceratopsians, such as the early Protoceratops and the famous Triceratops (below right).

Marginocephalia is one of three major groups of the Ornithischia, or "bird-hipped" dinosaurs. They are closely related to the Ornithopoda and some scientists suggest that the origin of Marginocephalia may lie within that group.

Pachycephalosaurus skull
Skull of Pachycephalosaurus at the Denver Museum of Nature & Science.
Triceratops skull
Visitors examine a Triceratops skull in the Valley Life Sciences Building, UC Berkeley campus.

Original page created by Brian Speer and John Hutchinson 12/1997; modifications since 2005 by David Smith. Pachycephalosaurus skull photo © 1996 Pamela J.W. Gore, Georgia Perimeter College. Triceratops skull photo by Dave Smith, © UCMP.