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 and David Jablonski in 1983 and was then expanded by Jablonski in 1986.[2]Paul Wignall and Michael Benton defined Lazarus taxa 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]
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The takahē of New Zealand had not been seen since 1898 when it was rediscovered in 1948.
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]
Lazarus taxa and other ghost lineages reflect the sporadic nature of the fossil record.
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 ghost lineage is a pronounced gap in time for the fossil record of a group, indicating that the group continued evolving throughout the gap, without direct fossil evidence from within the gap. Lazarus taxa are a type of ghost lineage where extinction was originally assumed to occur within the gap, only for younger fossils or surviving members of the group to indicate otherwise.
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.
In paleovirology, divergent clades of genomic elements from presumably extinct viruses are often known only from host genomes. However, in some cases extant viruses have later been associated with these "fossil" elements, indicating Lazarus-like taxa. For example, a clade of paleoviruses from presumed extinct filoviruses found in shrews was later found to contain an extant filovirus (Tapajós virus, TAPV).[7]
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.
From Quaternary (2.6 to 0 million years ago)
Chacoan peccary
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.[8]
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.[9]
False killer whale, first described by the British paleontologist and biologist Richard Owen based on a skull discovered in 1843 found in Stamford, Lincolnshire in England and dated to the Middle Pleistocene around 126,000 years ago. The first carcasses washed up on the shores of Kiel Bay in Denmark in 1861; until this point the species was thought to be extinct.
Bulmer's fruit bat (Aproteles bulmerae), originally described from a Pleistocene garbage pile, it was subsequently discovered alive elsewhere in its native New Guinea.[10]
The arboreal chinchilla rats (Cuscomys spp.), which were originally described based on a single species (Cuscomys oblativus) known only from archaeological remains discovered in ancient Inca tombs described in 1912 and believed to be extinct for almost a century. A second species (Cuscomys ashaninka) was discovered alive in Peru in 1999, and photographs taken at Machu Picchu in 2009 suggest that C.oblativus is still alive as well.
Majorcan midwife toad (Alytes muletensis), in the family Alytidae, described from fossil remains in 1977, discovered alive in 1979.
Mountain pygmy possum (Burramys parvus), first discovered in the fossil record in 1895; rediscovered alive in 1966.
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.[13]
From Neogene (23 to 2.6 million years ago)
Monito del monte
Nightcap oak (Eidothea hardeniana and Eidothea zoexylocarya), representing a genus previously known only from fossils 15 to 20million years old,[14] were recognized in 2000 and 1995,[15] respectively.
Laotian rock rat (Laonastes aenigmamus), a member of a family (Diatomyidae) thought to have gone extinct 11million years ago; found in 1996.[17]
Monito del monte (Dromiciops), sole surviving member of the order Microbiotheria; first described in 1894, thought to have gone extinct 11million years ago.
Submyotodon, a genus of bat originally known from a single fossil species (S. petersbuchensis) described in 2003 from the Miocene of Germany, about 11 to 16 million years ago. In 2015, a phylogenetic analysis of bats from Taiwan and China found three species previously classified in Myotis (M.caliginosus, M.latirostris, and M.moupinensis) to be wholly distinct from any other member of Myotis, and instead more closely allied to the fossil Submyotodon, and thus reclassified them in Submyotodon, making the genus extant once more.[18][19]
Dawn redwood (Metasequoia), a genus of conifer, described as a fossil in 1941, rediscovered alive in 1944.
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.[20]
Coelacanth (Latimeria), a member of a subclass (Actinistia) thought to have gone extinct 66million years ago; live specimens found in 1938.[21]
Alavesia, a genus of Atelestid fly, originally discovered as a fossil in amber over 100million years old in 1999, living species found in Namibia in 2010.
From Devonian (419 to 359 million years ago)
Monoplacophora
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.[22]
From Cambrian (539 to 485 million years ago)
Schinderhannes bartelsi, an extinct Devonian member of the order Radiodonta. The discovery of its fossils in Devonian was astonishing because previously, radiodonts were known only from the Cambrian, 100million years earlier.[23]
Mount Diablo buckwheat (Eriogonom truncatum), in the family Polygonaceae; thought to be extinct around 1935, but found again in 2005, then again in 2016.
Takhtajania perrieri, a genus of flowering plants in the family Winteraceae; first collected in 1909, rediscovered, and reclassified multiple times between 1963 and 1997.
Virginia round-leaf birch (Betula uber), a rare species of tree in the birch family; first discovered in 1914, thought to be extinct until 1975
Yellow fatu (Abutilon pitcairnense), a species of plant in the family Malvaceae. The plant was once considered extinct until 2003.
Tsori, a distinct and recently discovered species of Commiphora that was grown from an ancient seed found in excavations in the Judean Desert, replanted in 2009, and reached maturity in 2024.
Cultivars
Judean date palm, a distinct cultivar of date palm that disappeared around the 14th century, seeds dated from between 155BC to 64AD were found in the 1960s and were replanted in 2005.
Montreal melon, a common commercial plant in the 19th century that disappeared in the 1920s but was rediscovered after a couple of generations in a seed bank in 1996, replanted in 2024.
Sponges
Neptune's Cup (Cliona patera), a species of demosponge in the family Clionaidae; thought to be extinct from overharvesting in 1908, rediscovered in 2011.[24]
Lord Howe Island stick insect (Dryococelus australis); a species of stick insect in the family Phasmatodae; thought to be extinct by 1920, rediscovered in 2001.
Canterbury knobbed weevil (Hadramphus tuberculatus), in the family Curculionidae; first discovered in 1877, last seen in 1922 until it was rediscovered in 2004.
The cloaked bee (Pharohylaeus lactiferus); a bee in the subfamily Hylaeinae which had not been found since 1923 and was rediscovered in 2018.[27]
Lestes patricia, a species of damselfly discovered in 1924. Only a single male specimen was collected during the discovery. The species was left unseen until 2020 where a colony of them was rediscovered.
Megachile pluto, the world's largest bee. Not seen after 1858, when it was first collected, until it was rediscovered in 1981.[28]
Dinosaur ant (Nothomyrmecia macrops), a rare genus of ants consisting of a single species, discovered in 1931, not seen again until 1977.
Petasida ephippigera, a species of grasshopper in the family Pyrgomorphidae; thought to be extinct from 1900 until 1971, when a single male specimen was spotted, followed by a breeding pair shortly afterwards.
Schizodactylus inexspectatus, a dune-inhabiting cricket from Turkey, known from a single specimen seen in 1901 and presumed extinct until it was found again in 2005.
Bone skipper fly (Thyreophora cynophila), in the family Piophilidae; first described (1794) and last seen in Central Europe (1850), before being photographed in Spain in 2009.[29]
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 Saiko Lake in 2010, having survived after prior conservation efforts had introduced it there.
Shark
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.
Ganges shark (Glyphis gangeticus), the world's sole freshwater shark found in the Ganges River and Brahmaputra River in India and Bangladesh; previously only known from three museum specimens caught in the early 19th century, but was rediscovered at a fish market in Mumbai in February 2016.
Armoured frog (Litoria lorica), a species of frog in the family Hylidae; first discovered in 1976, until its rediscovery in 2008.
Ansonia latidisca (Sambas stream toad, Borneo rainbow toad) in the family Bufonidae; first discovered in 1924, until its rediscovery in 2011.
Starry night toad (Atelopus arsyecue), not seen for over 30 years until rediscovery in 2019.
Painted frog (Atelopus ebenoides marinkellei), a species of true toad in the family Bufonidae, believed to be extinct since 1995, until it was rediscovered in 2006.
Atelopus ignescens (Jambato toad, Quito stubfoot toad), a species of toad in the family Bufonidae; thought to be extinct since its last recorded sighting in 1988, until its rediscovery in 2016.[32]
Hula painted frog (Discoglossus nigriventer), the only living member of the genus Latonia; thought to be extinct in the 1950s, until it was rediscovered in 2011.
American cinchona plantation treefrog (Isthmohyla rivularis), a rare species of frog in the family Hylidae; thought to have become extinct, until its rediscovery in 2007.
Bolivian Cochran frog (Nymphargus bejaranoi), not seen for over 18 years until its rediscovery in early 2020.
Black jumping salamander (Ixalotriton niger), a species of salamander in the family Plethodontidae; believed to be extinct, until rediscovered in 2000 and again in 2006 and 2007.
Confusing rocket frog (Ectopoglossus confusus), thought to be extinct in 1989 until it was rediscovered in 2016.[33]
Large-crested toad (Incilius cristatus), a critically endangered species of true toad in the family Bufonidae.
Philautus chalazodes (chalazodes bubble-nest frog, white-spotted bush frog or Günther's bush frog), a species of frog in the family Rhacophoridae; no verifiable reports of this species, until its rediscovery in 2011.
Guttman's Stream frog (Pulchrana guttmani)
Sumatra toad (Bufo sumatranus), a species of toad in the family Bufonidae.
Attenborough's long-beaked echidna (Zaglossus attenboroughi), echidna species found in Cyclops Mountains of Papua New Guinea; formerly last seen in 1962 and believed to be possibly extinct, until it was recorded again in November 2023.[34]
Baiji(Lipotes vexillifer), a freshwater dolphin found in the Yangtze River in China; it was declared functionally extinct in 2006 after a month long expedition failed to locate one, but it has been photographed and seen by Chinese locals in 2007, 2016, 2018, and 2024.
Bavarian pine vole (Microtus bavaricus), is a vole in the family Cricetidae; believed extinct in the 1960s, until it was rediscovered in 2000.
Black-footed ferret (Mustela nigripes), a North American species presumed extinct in 1979 until it was rediscovered in 1981. A captive breeding program of the discovered ferrets successfully reintroduced the species into the wild.
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.
Bouvier's red colobus (Piliocolobus bouvieri), a species of colobus monkey rediscovered in 2015.
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 3400BCE, but it was rediscovered in the 1960s.
Zyzomys pedunculatus (known by a variety of names, including central rock rat, central thick-tailed rock-rat, Macdonnell Range rock-rat, Australian native mouse, rat à grosse queue or rata coligorda), a single 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 cubana), thought to have been extinct until a live specimen was found in 2003.
Humboldt marten (Martes caurina humboldtensis), subspecies of the Pacific marten thought to be extinct until rediscovered in 1996 on remote camera traps in the Six Rivers National Forest in northern California.
Julia Creek dunnart (Sminthopsis douglasi), thought to be extinct until it was rediscovered in the 1990s.
Mahogany glider (Petaurus gracilis), described in 1883 and not formally recorded between 1886 and 1989.[35] An expedition by the Queensland Museum in 1989 found a living population.[36]
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.[37]
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.[38]
Tammar wallaby (Macropus eugenii), the mainland Australian subspecies was presumed extinct from 1925 until genetically matched with invasive wallabies in New Zealand in 1998.
Vietnam mouse-deer (Tragulus versicolor), last known from a specimen acquired from hunters in 1990, not seen again for nearly 30 years until multiple individuals were sighted with camera-trap photographs in a 2019 survey of prospective habitat.
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.
Terror skink (Phoboscincus bocourti), a 50-cm-long lizard, was previously known from a single specimen captured around 1870 and was long presumed extinct. In 2003, on a tiny islet, it was rediscovered.
Fernandina Island Galápagos tortoise (Chelonoidis phantasticus), only known from a single male specimen in 1906 and putative droppings and bite marks throughout the 20th century up to the 2010s. A female individual was rediscovered on the island on an expedition in 2019 for the Animal Planet show Extinct or Alive.[41]
Bermuda petrel or "cahow" (Pterodroma cahow), thought extinct since 1620 until 18 nesting pairs were found in 1951 on an uninhabited rock outcropping in Bermuda. Bermudian David B. Wingate has devoted his life to bringing the birds back, and in the 2011—12 breeding season they passed 100-pairs.[43]
Chinese crested tern (Thalasseus bernsteini), feared extinct in the mid-late 20th century for over 6 decades until a small breeding colony was found in 2000.[44]
Ivory-billed woodpecker (Campephilus principalis), the "Lord God Bird", thought extinct circa 1987 before unconfirmed sightings in 1999, 2004, and 2006 in Arkansas and Florida.[45]
Kaempfer's woodpecker (Celeus obrieni), a Brazilian woodpecker feared extinct after no specimen had been found since its discovery in 1926. Rediscovered in 2006.
Large-billed reed-warbler (Acrocephalus orinus), a warbler rediscovered in Thailand in 2006, previous known only from a specimen collected in India in 1867.
Takahē (Porphyrio hochstetteri), assumed extinct in 1898 but found again in 1948.
Utila chachalaca (Ortalis vetula deschauenseei), subspecies of the plain chachalaca from Honduras, not recorded between 1963 and 2000 and confirmed photographically in 2005.
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.[47]
Because its definition is ambiguous, some, like R. B. Rickards and A. J. Wright, reject the very concept of the Lazarus taxon. Rickards and Wright have questioned the usefulness of the concept, writing 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.[48] They have argued that accurate plotting of biodiversity changes and species abundance through time, coupled with an appraisal of their palaeobiogeography, is more important than using this title to categorize species.[48]
The lack of public engagement around environmental issues 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.[49] 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.[50]
Ryan, Gerard; Baker, Christopher (November 2016). "A general method for assessing the risks and benefits of secrecy in conserving 'Lazarus species'". Biological Conservation. 203: 186–187. Bibcode:2016BCons.203..186R. doi:10.1016/j.biocon.2016.09.022.
Messer, A. C. (1984). "Chalicodoma pluto: The World's Largest Bee Rediscovered Living Communally in Termite Nests (Hymenoptera: Megachilidae)". Journal of the Kansas Entomological Society. 57 (1): 165–168. JSTOR25084498.
Miguel Carles-Tolrá, Pablo C. Rodríguez & Julio Verdú (2010). "Thyreophora cynophila (Panzer, 1794): collected in Spain 160 years after it was thought to be extinct (Diptera: Piophilidae: Thyreophorini)". Boletín de la Sociedad Entomológica Aragonesa (S.E.A.) 46: 1–7.
De Vosjoli, Phillipe; Repashy, Allen; Fast, Frank (2003). Rhacodactylus: The Complete Guide to their Selection and Care. Advanced Vivarium Inc. ISBN978-0-9742971-0-1.
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