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 Gospel of John, in which Jesus is claimed to have raised Lazarus from the dead. Lazarus taxa occur either because of (local) extinction, later resupplied, or as a sampling artifact. The fossil record is 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.
The concept was developed in palaeontology where, after a major extinction event, some groups reappear after millions of years. The usual explanation is that numbers were driven so low that their chance of fossilisation were extremely low. Then, gradually, their numbers revived.
History of the idea[change | edit source]
In 1974 Batten pointed out that the Lower Triassic record lacked genera and species which had been present in the Permian, but which reappeared 20 million years later in the Middle Triassic. Jablonski later coined the term 'Lazarus taxon' for species and genera which disappear from the fossil record, only to reappear later when conditions return to normal.
Living examples[change | edit source]
There are some well-known examples of it happening to present-day species.
Some well-known examples:
- A complete clade of lobe-finned fish, the sub-class Coelacanthimorpha, was thought to have gone extinct 80 million years ago. Then a Coelacanth (Latimeria), was found in 1938.
- The Monoplacophora, a class of molluscs were believed to have gone extinct in the middle Devonian (~380 million years ago) until living members were discovered in deep water off Costa Rica in 1952.
- Dawn Redwood or Metasequoia, a genus of conifer, was first described as a fossil from the Mesozoic era by Shigeru Miki in 1941, but in 1944 a small stand was discovered in Modaoxi, China.
- Mountain Pygmy Possum (Burramys parvus), Australia's only truly hibernating marsupial, known originally from the fossil record, was discovered in 1966.
References[change | edit source]
- Batten R.L. 1973. The vississitudes of the gastropods during the interval of Guadalupian–Ladinian time.In A. Logan & L.V. Hills (eds) The Permian and Triassic systems and their mutual boundary. Memoir 2, 596–607. Calgary, Canadian Society of Petroleum Geologists.
- Jablonski D. 1986. Background and mass extinctions: alternation of macroevolutionary regimes. Science 231, 129–133.