The Aftermath of the Extinction

The Late Devonian extinction precipitated a permanent change in the structure of the global metazoan reef component of marine ecosystems in geologic time. Metazoan reef ecosystems were virtually destroyed in the extinction, shrinking in geographic extent by a factor of 5,000 from the Frasnian world to the Famennian. The stromatoporoids were a keystone taxon in the ecological structure of Devonian reefs, and the three-dimensional physical structures created by the stromato-poroids provided the reefal niches crucial to the existence of many other benthic taxa. The failure of the previously diverse tabulate corals to recover following the Late Devonian extinction was directly linked to the loss of the spatial heterogeneity and structure provided by the stromatoporoids.

Other ecological effects of the Late Devonian extinction are not as dramatic as the demise of benthic reefal ecosystems but are just as permanent. In the marine zooplankton, all of the cricoconarids were lost, representing an extinction at the class level in the taxo-nomic hierarchy. The cricoconarids were tiny cone-shaped animals, similar to modern plank-tic snails, and their extinction eliminated a major element of the Devonian zooplankton. In the nekton, the collapse of the hot climates of the Frasnian struck the marine fish much harder than their freshwater relatives, which were better adapted to seasonal temperature fluctuations; fully one-third of all placoderm fish families were driven out of the world's oceans by the climatic effects of the Late Devonian extinction.

See also: Coral Reefs; Cretaceous-Tertiary Extinction; Global Climate Change; Mass Extinction; Permo-Triassic Extinction; Volcanoes

Bibliography

McGhee, George R. 1996. The Late Devonian Mass Extinction. New York: Columbia University Press; McGhee, George R. 2001. "Late Devonian Extinction." In Palaeobiology II, edited by Derek E. G. Briggs and Peter R. Crowther, pp. 223-226. Oxford: Blackwell Science; Hallam, Anthony, and Paul B. Wignall. 1997. Mass Extinctions and Their Aftermath. Oxford: Oxford University Press; Racki, Grzegorz. 1998. "Frasnian-Famennian Biotic Crisis: Undervalued Tectonic Control?" Palaeogeography, Palaeoclimatology, Palaeoecology 141:177-198.

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