Lazarus Taxon
In the field of paleontology, the term Lazarus taxon refers to an intriguing phenomenon where a taxon, which appears to have vanished from the fossil record for one or more periods, reappears in later records or as living organisms. This concept is named after Lazarus of Bethany, who, according to the Bible, was raised from the dead by Jesus Christ. The reappearance of such taxa often occurs in isolated, specialized, or obscure habitats, making them appear as though they have returned from extinction.
Characteristics and Examples
Lazarus taxa challenge our understanding of extinction and survival, providing insights into evolutionary biology and conservation. They can be considered a type of ghost lineage, where it was originally assumed that extinction occurred within a gap in records, only for subsequent evidence to indicate otherwise. These taxa often reflect survival through extreme rarity and the eventual rebound after periods of presumed extinction.
One of the most famous examples is the coelacanth, a fish thought to have gone extinct approximately 66 million years ago, until it was found alive off the coast of South Africa in 1938. Similarly, the Wollemi pine was known only from fossils until living specimens were discovered in Australia in 1994.
Related Phenomena
The concept of a Lazarus taxon is sometimes confused with other phenomena:
- Elvis taxon: This term refers to a look-alike species that emerges after the extinction of the original taxon through convergent evolution.
- Zombie taxon: A taxon where specimens have been collected from strata younger than the supposed extinction period, often due to reworking of older fossils into younger sediments.
- Living fossil: An extant taxon that appears largely unchanged from its ancient fossilized ancestors, although living fossils may occur regularly in the fossil record, unlike Lazarus taxa.
Importance in Paleontology and Conservation
Lazarus taxa highlight the limitations and complexities of the fossil record, as only a small fraction of organisms are fossilized, and even fewer are discovered before destruction. This sporadic nature can lead to gaps not necessarily caused by extinction, particularly when the population is very low. After mass extinction events, such as the Permian–Triassic extinction event, many taxa exhibiting the Lazarus effect have been observed.
The concept was first coined by Karl W. Flessa and David Jablonski in 1983, and further elaborated by Jablonski in 1986. Their work underscores the importance of recognizing reemergence patterns and survival strategies that taxa employ, even in the face of extreme environmental challenges.