Epoccipital

Triceratops head from the front, with a fringe of epoccipitals around the frill.
Epoccipitals, marked by 4 on a Triceratops prorsus skull.

Epoccipital is an anatomical term for the distinctive bones found lining the frills of ceratopsid dinosaurs. The name is a misnomer, as they are not associated with the occipital bone.[1] Epoccipitals begin as separate bones that fuse during the animal's growth to either the squamosal or parietal bones that make up the base of the frill. These bones were ornamental instead of functional, and may have helped differentiate species. Epoccipitals probably were present in all known ceratopsids with the possible exception of Zuniceratops.[2] They appear to have been broadly different between short-frilled ceratopsids (centrosaurines) and long-frilled ceratopsids (chasmosaurines), being elliptical with constricted bases in the former group, and triangular with wide bases in the latter group. Within these broad definitions, different species would have somewhat different shapes and numbers. In centrosaurines especially, like Centrosaurus, Pachyrhinosaurus, and Styracosaurus, these bones become long and spike- or hook-like.[3] A well-known example is the coarse sawtooth fringe of broad triangular epoccipitals on the frill of Triceratops. When regarding the ossification's morphogenetic traits, it can be described as dermal.

The term epoccipital was coined by famous paleontologist Othniel Charles Marsh in 1889.[4][1]

References

  1. ↑ 1.0 1.1 Dodson, Peter (1996). The Horned Dinosaurs. Princeton University Press, Princeton, New Jersey. pp. 49, 63. ISBN 0-691-02882-6.
  2. ↑ Makovicky, Peter J. (2012). "Marginocephalia". In M. K. Brett-Surman, Thomas R. Holtz, James O. Farlow (eds.). The Complete Dinosaur (2. ed.). Indiana University Press. p. 540. ISBN 978-0-253-35701-4.
  3. ↑ Dodson, Peter; Forster, Catherine. A; Sampson, Scott D. (2004). "Ceratopsidae". In Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 494–513. ISBN 0-520-24209-2.
  4. ↑ Marsh, Othniel C. (1889). "The skull of the gigantic Ceratopsidae.". American Journal of Science, 3rd Series 38: 501–506.