Lazarus taxon
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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 New Testament figure Lazarus, who was raised 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 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 reoccurring IUCN Red List species for example). Examples include the Wollemi Pine, the Jerdon's Courser, the Ivory-billed Woodpecker, and the Takahe, a flightless bird endemic to New Zealand. It should be noted however, that "being extinct" strongly relates to the sampling intensity, the whims of the IUCN, and that the period of apparent extinction is too short to be designated as "Lazarus taxa" (in its paleontological meaning).
Lazarus taxa that reappear in nature after being known only as fossils can be seen as an informal subcategory of the journalist's "living fossils" (without the conditions needed of being designated as a living fossil). On the other hand, all species "considered living fossils" (and this a point of contention) are lazarus taxa de facto. If they do not meet the criteria of living fossils, it is possible they are Elvis taxa.
Reappearing red list species
- Madeiran land snail (Discus guerinianus) — Extinct in 1996 — Found again in 1999
- Fernandina rice rat (Nesoryzomys fernandinae) — Extinct in 1996 — Found again in late 1990s
- Ivory-billed Woodpecker (Campephilus principalis) — Extinct in 1994 — Sighted in 1999, found again in 2005.
- Lord Howe Island stick insect (Dryococelus australis)
- Bavarian pine vole (Microtus bavaricus)
- Mount Diablo buckwheat (Eriogonom truncatum) — Extinct around 1935 — Found again in 2005