Lazarus taxa

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The takahe is an example of a Lazarus taxon.
The takahe is an example of a Lazarus taxon.

In paleontology, a Lazarus taxon (plural taxa) is a taxon that disappears from one or more periods of the fossil record, only to appear again later. The term refers to the account in the Gospel of John chapter 11 in which Jesus miraculously raises Lazarus from the dead. Lazarus taxa are observational artifacts that appear to occur either because of (local) extinction, later resupplied, or as a sampling artifact. If the extinction is conclusively found to be total (global or worldwide) and the supplanting species is not a lookalike (an Elvis species), the observational artifact is overcome. The fossil record is inherently imperfect (only a very small fraction of organisms become fossilized) and contains gaps not necessarily caused by extinction, particularly when the number of individuals in a taxon becomes very low. If these gaps are filled by new fossil discoveries, a taxon will no longer be classified as a Lazarus taxon.

The terms "Lazarus effect" or "Lazarus species" have also found some acceptance in neontology — the study of extant organisms, as contrasted with paleontology — as an organism that is rediscovered alive after having been widely considered extinct for years (a recurring IUCN Red List species for example). Examples include the Wollemi pine, the Jerdon's courser, the ivory-billed woodpecker (disputed), the Mahogany Glider and the takahē, a flightless bird endemic to New Zealand.[1] It should be noted, however, that being "extinct" strongly relates to the sampling intensity and the whims of the IUCN, and that such a period of apparent extinction is too short for species to be designated as "Lazarus taxa" (in its paleontological meaning).

Lazarus taxa that reappear in nature after being known only as old enough fossils can be seen as an informal subcategory of the journalist's "living fossils", because a taxon cannot become globally extinct and reappear. If the original taxon went globally extinct, the new taxon must be an Elvis taxon. On the other hand, all species "correctly considered living fossils" (with all conditions fulfilled, living and found through a considerable part of the geologic timescale) cannot be Lazarus taxa.

Contents

Reappearing species

Reappearing IUCN red list species

Reappearing fossil taxa

Coelacanth Latimeria chalumnae.
Coelacanth Latimeria chalumnae.


See also

References

  1. ^ Shuker, Karl P N (2002). The New Zoo: New and Rediscovered Animals of the Twentieth Century. House of Stratus. 
  2. ^ C.A. McGuinness (2004). Xylotoles costatus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 17 March 2007.

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  • This page was last modified on 7 September 2008, at 17:28.

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