- Arcto-Tertiary Geoflora
The Arcto-Tertiary Geoflora is a hypothesized
flora l assemblage that once covered theNorthern Hemisphere , from roughly the lateMesozoic to midCenozoic Era s.Origins
First proposed by the paleobotanists
J.S. Gardner andC. Ettinghausen in1879 , the concept was intended to answer questions about thedisjunct distribution of identical or closely-relatedplant species : for instance,magnolia andtulip tree s are native to both theSoutheast United States and southernChina andIndochina . [Delcourt, Hazel, "Forests in Peril", (Blacksburg: The McDonald and Woodward Publishing Company, 2002), 31-2.] , [Dougal Dixon et al., "The Atlas of Life on Earth", (New York: Barnes & Noble Books, 2001), 334-5.]As envisioned, the ATG had a wide distribution when the global climate was much warmer than it is currently, a situation strengthened by the closer position of some of the continents in late Mesozoic to early Cenozic times. [Delcourt, 31.] , [Dixon et al., 334.] With the onset of global cooling and the
Ice Age s, the ranges of thesetropical tosubtropical species were left in isolated pockets of warmer climates. [Delcourt, 32.]The southern, more tropical equivalent of the ATG was the Neotropical Tertiary Geoflora. [Ibid.]
Footnotes:
External links
* http://www.radford.edu/~swoodwar/CLASSES/GEOG235/biomes/tbdf/arcto.html
Wikimedia Foundation. 2010.