The base of the Campanian Stage is defined as a place in the stratigraphic column where the extinction of crinoid species Marsupites testudinarius is located. A GSSP was ratified for the base of the Campanian in October 2022, having been placed in Bottaccione, Gubbio, Italy.[2] The top of the Campanian stage is defined as the place in the stratigraphic column where the ammonitePachydiscus neubergicus first appears.[5]
Subdivisions
The Campanian can be subdivided into Lower, Middle and Upper Subages. In the western interior of the United States, the base of the Middle Campanian is defined as the first occurrence of the ammonite Baculites obtusus (80.97 Ma) and the base of the Upper Campanian defined as the first occurrence of the ammonite Didymoceras nebrascense (76.27 Ma).[10] In the Tethys domain, the Campanian encompasses six ammonite biozones. They are, from young to old:[11]
During the Campanian age, a radiation among dinosaur species occurred. In North America, for example, the number of known dinosaur genera rises from four at the base of the Campanian to forty-eight in the upper part. This development is sometimes referred to as the "Campanian Explosion". However, it is not yet clear if the event is artificial, i.e. the low number of genera in the lower Campanian can be caused by a lower preservation chance for fossils in deposits of that age. The generally warm climates and large continental area covered in shallow sea during the Campanian probably favoured the dinosaurs. In the following Maastrichtian stage, the number of North American dinosaur genera found is 30% less than in the upper Campanian.[12]
^Hancock, J.M.; Gale, A.S. (1996). "The Campanian Stage"(PDF). Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre. 66: 103–109. Retrieved 27 September 2021.
^Ogg, J. G.; Hinnov, L. A.; Huang, C. (2012-01-01), Gradstein, Felix M.; Ogg, James G.; Schmitz, Mark D.; Ogg, Gabi M. (eds.), "Chapter 27 - Cretaceous", The Geologic Time Scale, Boston: Elsevier, pp. 793–853, doi:10.1016/b978-0-444-59425-9.00027-5, ISBN978-0-444-59425-9
Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42–57 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis, Indiana.
Weishampel, D.B.; Barrett, P.M.; Coria, R.A.; Le Loueff, J.; Xu, X.; Zhao, X.; Sahni, A.; Gomani, E.M.P. & Noto, C.N.; 2004: Dinosaur distribution, in: Weishampel, D.B.; Dodson, P. & Osmólska, H. (eds.): The Dinosauria, University of California Press, Berkeley (2nd ed.), ISBN0-520-24209-2, pp 517–606.