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In paleontology, a Lazarus taxon (plural taxa) is a taxon that disappears for one or more periods from the fossil record, only to appear again later. Likewise in conservation biology and ecology, it can refer to species or populations that were thought to be extinct, and are rediscovered.[1] The term Lazarus taxon was coined by Karl W. Flessa; & David Jablonski in 1983 and was then expanded by Jablonski in 1986.[2] Wignall and Benton defined Lazarus taxon as, ‘At times of biotic crisis many taxa go extinct, but others only temporarily disappeared from the fossil record, often for intervals measured in millions of years, before reappearing unchanged’.[3] Earlier work also supports the concept though without using the name Lazarus taxon, like work by Christopher R. C. Paul.[4]

The term refers to the story in the Christian biblical Gospel of John, in which Jesus Christ raised Lazarus from the dead.

Potential explanations


Lazarus taxa are observational artifacts that appear to occur either because of (local) extinction, later resupplied, or as a sampling artifact. The fossil record is inherently sporadic (only a very small fraction of organisms become fossilized, and an even smaller fraction are discovered before destruction) and contains gaps not necessarily caused by extinction, particularly when the number of individuals in a taxon is very low.

After mass extinctions, such as the Permian–Triassic extinction event, the Lazarus effect occurred for many taxa. However, there appears to be no link with the abundance of fossiliferous sites and the proportion of Lazarus taxa, and no missing taxa have been found in potential refuges. Therefore, reappearance of Lazarus taxa probably reflects the rebound after a period of extreme rarity during the aftermath of such extinctions.[5]

Related but distinct concepts


An Elvis taxon is a look-alike that has supplanted an extinct taxon through convergent evolution.

A zombie taxon is a taxon that contains specimens that have been collected from strata younger than the extinction of the taxon. Later such fossils turn out to be freed from the original seam and refossilized in a younger sediment. For example, a trilobite that gets eroded out of its Cambrian-aged limestone matrix, and reworked into Miocene-aged siltstone.

A living fossil is an extant taxon that appears to have changed so little compared with fossil remains, that it is considered identical. Living fossils may occur regularly in the fossil record, such as the lampshell Lingula, though the living species in this genus are not identical to fossil brachiopods.[6]

Other living fossils however are also Lazarus taxa if these have been missing from the fossil record for substantial periods of time, such as applies for coelacanths.

Finally, the term "Lazarus species" is applied to organisms that have been rediscovered as being still alive after having been widely considered extinct for years, without ever having appeared in the fossil record. In this last case, the term Lazarus taxon is applied in neontology.

Reappearing fossil taxa


  • Bush dog (Speothos venaticus), last surviving species of the genus Speothos; first described as an extinct taxon in 1842 by Peter Wilhelm Lund, based on fossils uncovered from Brazilian caves; Lund found and described living specimens in 1843 without realizing they were of the same species as the fossils, dubbing the living bush dogs as members of the genus "Icticyon"; this was not corrected until some time in the 20th century.[7]
  • Chacoan peccary (Catagonus wagneri), last surviving species of the genus Catagonus; believed to be the closest living relative to the extinct genus Platygonus. First described as extinct in 1930 as fossils; live specimens found in 1974.[8]
  • Coelacanth (Latimeria), a member of a subclass (Actinistia) thought to have gone extinct 66 million years ago; live specimens found in 1938.[9]
  • Nightcap oak (Eidothea hardeniana and Eidothea zoexylocarya), representing a genus previously known only from fossils 15 to 20 million years old,[10] were recognized in 2000 and 1995,[11] respectively.
  • Gracilidris, a genus of dolichoderine ants thought to have gone extinct 15–20 million years ago was found in Paraguay, Brazil, and Argentina and rediscribed in 2006.[12]
  • Laotian rock rat (Laonastes aenigmamus), a member of a family (Diatomyidae) thought to have gone extinct 11 million years ago; found in 1996.[13]
  • Majorcan midwife toad (Alytes muletensis), in the family Alytidae, described from fossil remains in 1977, discovered alive in 1979.
  • Dawn redwood (Metasequoia), a genus of conifer, described as a fossil in 1941, rediscovered alive in 1944.
  • Monito del monte (Dromiciops), sole surviving member of the order Microbiotheria; first described in 1894, thought to have gone extinct 11 million years ago.
  • Bulmer's fruit bat (Aproteles bulmerae), originally described from a Pleistocene garbage pile, it was subsequently discovered alive elsewhere in its native New Guinea.[14]
  • Monoplacophora, a class of molluscs believed to have gone extinct in the middle Devonian Period (c. 380 million years ago) until living members were discovered in deep water off Costa Rica in 1952.[15]
  • Mountain pygmy possum (Burramys parvus), first discovered in the fossil record in 1895; rediscovered alive in 1966.
  • Schinderhannes bartelsi, a Devonian member of the family Anomalocarididae, previously known only from Cambrian fossils, 100 million years earlier.
  • Wollemi pine (Wollemia), a genus of coniferous tree in the family Araucariaceae; previously known only from fossils from 2 to 90 million years ago, rediscovered in 1994.[16]
  • Calliostoma bullatum, a species of deepwater sea snail; originally described in 1844 from fossil specimens in deep-water coral-related sediments from southern Italy, until extant individuals were described in 2019 from deep-water coral reefs off the coast of Mauritania.[17]

Reappearing IUCN red list species


  • Judean date palm, found as a seed dated from between 155 BC to 64 AD, replanted in 2005.
  • Montreal melon, a common plant in the 19th century that disappeared but was rediscovered after a couple of generations in 1996.
  • Black kokanee (Oncorhynchus nerka kawamurae), a Japanese species of salmon in the family Salmonidae; believed extinct in 1940 after attempts at conservation seemingly failed. The species was rediscovered in Lake Saiko in 2010.
  • Smoothtooth blacktip shark (Carcharhinus leiodon), a species of requiem shark, in the family Carcharhinidae; known only from a specimen caught in 1902, the shark was rediscovered at a fish market in 2008.
  • Bavarian pine vole (Microtus bavaricus), is a vole in the family Cricetidae; believed extinct in the 1960s, until it was rediscovered in 2000.
  • Brazilian arboreal mouse (Rhagomys rufescens), a South American rodent species of the family Cricetidae; first described in 1886, was believed to be extinct for over one hundred years.
  • Onychogalea fraenata (Bridled nail-tail wallaby, bridled nail-tailed wallaby, bridled nailtail wallaby, bridled wallaby, merrin or flashjack), a vulnerable species of macropod; thought to be extinct since the last confirmed sighting in 1937, but rediscovered in 1973.
  • Caspian horse (Khazar horse), thought to be descended from Mesopotamian horses; remains dating back to 3400 B.C.E, but it was rediscovered in the 1960s.
  • Zyzomys pedunculatus (central rock rat, central thick-tailed rock-rat, Macdonnell Range rock-rat, Australian native mouse, rat à grosse queue or rata coligorda), a species of rodent in the family Muridae; thought to be extinct in 1990 and 1994, until a reappearance in 2001 and in 2002, then the species went unrecorded until 2013.
  • Cuban solenodon (Atopogale cubanus), thought to have been extinct until a live specimen was found in 2003.
  • Dinagat bushy-tailed cloud rat, assumed extinct after discovery in 1974, but rediscovered in 2012.
  • Fernandina rice rat (Nesoryzomys fernandinae), thought extinct in 1996 (last seen 1980) but found again in the late 1990s.
  • Formosan clouded leopard (Neofelis nebulosa brachyura), Taiwanese leopard presumed extinct from the late 20th century until sighted in 2019.
  • Gilbert's potoroo (Potorous gilbertii), extremely rare Australian mammal presumed extinct from the 19th century until 1994.
  • Miller's grizzled langur (Presbytis hosei canicrus), presumed extinct 2010, rediscovered 2012.
  • Leadbeater's possum (Gymnobelideus leadbeateri), thought to be extinct until 1965.
  • Machu Picchu arboreal chinchilla rat (Cuscomys oblativus), believed extinct since the 1400s or 1500s, but rediscovered in 2009 near Machu Picchu in Peru.
  • Mahogany glider (Petaurus gracilis), described in 1883 and not recorded between 1886 and 1973. An expedition by the Queensland Museum in 1989 found a living population.
  • New Guinea big-eared bat (Pharotis imogene), previously, the species was believed to have been extinct since 1890, when it was last spotted. In 2012, researchers realised that a female bat collected near Kamali was a member of this species.[24]
  • New Holland mouse (Pseudomys novaehollandiae), described by George Waterhouse in 1843, it was re-discovered in Ku-ring-gai Chase National Park, North of Sydney, in 1967.
  • Philippine naked-backed fruit bat (Dobsonia chapmani), in 1996 the species was declared extinct by the IUCN, as none had been sighted since 1964, but the bat was rediscovered in 2000.[25]
  • Roosevelt's muntjac (Muntiacus rooseveltorum), it was re-discovered in Xuan Lien Nature Reserve in Vietnam's Thanh Hoa province in 2014.
  • San Quintin kangaroo rat (Dipodoys gravipes), previously seen in 1986, feared extinct until rediscovery in 2017.[26]
  • Santiago Galápagos mouse (Nesoryzomys swarthi), thought extinct and last recorded in 1906, but was rediscovered in 1997.
  • Short-footed Luzon tree rat (Carpomys melanurus), believed extinct since 1896, but rediscovered in 2008 on Mount Pulag in northern Luzon.
  • Tammar wallaby (Macropus eugenii), the mainland Australian subspecies was presumed extinct from 1925 until genetically matched with invasive wallabies in New Zealand in 1998.
  • Woolly flying squirrel (Eupetaurus cinereus), known only from pelts collected in Pakistan in the late 19th century, until live specimens were collected in the 1990s.
  • Wimmer's shrew (Crocidura wimmeri), believed extinct since 1976, but rediscovered in 2012 in Côte d'Ivoire.
  • Yellow-tailed woolly monkey (Lagothrix flavicauda), first described from furs in 1812, live specimens not discovered until 1926.
  • Discus guerinianus, a Madeiran land snail thought extinct in 1996 but found again in 1999.
  • Greater Bermuda land snail (Poecilozonites bermudensis), last recorded sighting made in the early 1970s, survey in 1988 and studies in 2000, 2002, and 2004 seemed to confirm extinction, rediscovered in City of Hamilton alleyway in 2014.[31]
  • Elliptio nigella (recovery pearly mussel)

Discussions


Because the definition of a Lazarus taxon is ambiguous, some like R. B. Rickards, do not agree with the existence of a Lazarus taxon.

Rickards and Wright questioned the usefulness of the concept of a Lazarus taxon. They wrote in "Lazarus taxa, refugia and relict faunas: evidence from graptolites" that anyone could argue that any gap in the fossil record could potentially be considered a Lazarus effect because the duration required for the Lazarus effect is not defined.[32] They believed accurate plotting of biodiversity changes and species abundance through time, coupled with an appraisal of their palaeobiogeography was more important than using this title to categorize species.[32]

Communication and education


The lack of public engagement around environmental issue has led conservationists to attempt newer communication strategies. One of them is the focus on positive messages, of which Lazarus species are an important part [33] One conservation outreach project that has focused exclusively on species rediscoveries is the Lost & Found project which aims to tell the stories of species once thought extinct but that were subsequently rediscovered.[34]

See also


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