A Lazarus taxon is an animal or plant which disappears from the fossil record, presumably because it is extinct, and then reappears. In some cases, an animal which is thought to be totally extinct may be spotted and described alive, sometimes millions of years after the last fossil evidence of the species has vanished. This illustrates the unreliability of the fossil record; a special set of circumstances must come together for a fossil to form, making fossilization extremely rare.
This term references the New Testament story in which Jesus raises Lazarus from the dead. In order to be identified as a Lazarus taxon, the fossil record must have a significant gap, indicating that the animal appeared to lapse into extinction for whatever reason before reappearing. Some examples of Lazarus taxa thought to be extinct which showed up alive include the takahe in New Zealand, the ivory-billed woodpecker, Mount Diablo buckwheat, and the coelacanth.
In most cases, when a Lazarus taxon is discovered alive after being previously thought extinct, it may be in a critical status. Individual representatives of the species usually survive because they found an isolated area, such as the remote valley where the takahe was found, and the gene pool may be extremely small. If the animal's habitat is disturbed, it could prove to be the permanent end of the species.
When a Lazarus taxon is found alive and kicking, it is often cause for great excitement among scientists. Lazarus taxa are interesting biologically because they lead people to speculate about what happened to the animal or plant and why, and because they can reveal clues about previous eras of life on Earth. Many people also find the re-emergence of species believed extinct to simply be exciting, as well they should; the existence of Lazarus taxa shows that the Earth always has a few surprises in store.
A closely related concept is the Elvis taxon, or Elvis species. An Elvis species is a look-alike; due to convergent evolution, it has developed a similar appearance and lifestyle to an extinct species. As a general rule, Elvis taxa are not biologically related to their extinct counterparts. Sometimes, an Elvis taxon may be misidentified as a Lazarus taxon, until research reveals the truth.