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Living fossil is an informal term for any living species (or clade) of organism which seems to be the same as a species otherwise only known from fossils and has no close living relatives. These species have all survived major extinction events, and generally retain low taxonomic diversities. A species which successfully radiates (forming many new species after a possible genetic bottleneck) has become too successful to be considered a "living fossil". The term is frequently misinterpreted, however. Image File history File links Broom_icon. ... In biology, a species is one of the basic units of biodiversity. ... A clade is a term belonging to the discipline of cladistics. ... Three small ammonite fossils, each approximately 1. ... An extinction event (also known as: mass extinction; extinction-level event, ELE) occurs when there is a sharp decrease in the number of species in a relatively short period of time. ... A population bottleneck (or genetic bottleneck) is an evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented from reproducing, and the population is reduced by 50% or more, often by several orders of magnitude. ...

There is a subtle difference between a "living fossil" and a "Lazarus taxon". A Lazarus taxon is a taxon (either one species or a group of species) that suddenly reappears, either in the fossil record or in nature (i.e. as if the fossil had "come to life again"), while a living fossil is a species that (seemingly) hasn't changed during its very long lifetime (i.e. as if the fossil has always lived). The mean species turnover time (the time a species lasts before it is replaced) varies widely among the phyla, but is about 2-3 million years. So, a living species that was thought to be extinct (e.g. the coelacanth, Latimeria chalumnae) is not a living fossil simply due to that definition (though it may still be one because it hasn't changed much), it is a Lazarus species. Coelacanths disappeared from the fossil record some 80 million years ago (upper Cretaceous). If, however, other Cenozoic Latimeria fossil species were to be found, the coelacanth would be considered a true living fossil, as that would fill in the gap where the species is "dead". Of course, species do not just appear out of thin air, so all living Lazarus species (excluding disappearing and reappearing red list species) are nonetheless considered living fossils, if it can be shown they are not Elvis taxa. The takahe is an example of a Lazarus taxon. ... A taxon (plural taxa), or taxonomic unit, is a grouping of organisms (named or unnamed). ... Biological systematics is the study of the diversity of life on the planet earth, both past and present, and the relationships among living things through time. ... Phylum (plural: phyla) is a taxon used in the classification of animals, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... This article or section does not cite its references or sources. ... The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... The Cenozoic Era (IPA pronunciation: ); sometimes Caenozoic Era in the United Kingdom) meaning new life (Greek kainos = new + zoe = life) is the most recent of the three classic geological eras. ... The IUCN Red List of Threatened Species (also known as the IUCN Red List and Red Data List), created in 1963, is the worlds most comprehensive inventory of the global conservation status of plant and animal species. ... In paleontology, an Elvis taxon (plural taxa) is a taxon which has been misidentified as having re-emerged in the fossil record after a period of extinction, but is not actually a descendant of the original taxon, instead having developed a similar morphology through convergent evolution. ...

Some living fossils are species that were known from fossils before living representatives were discovered. The most famous examples of this are the coelacanthiform fishes Latimeria chalumnae and Latimeria menadoensis and the dawn redwood, Metasequoia, discovered in a remote Chinese valley. Others include glypheoid lobsters, mymarommatid wasps, and jurodid beetles, all of which were first described from fossils, but later found alive (2 species, 10 species, and one species respectively). Others are a single living species with no close living relatives, but which is the survivor of a large and widespread group in the fossil record, perhaps the best-known example of which is Ginkgo biloba (the ginkgo), though there are others, such as the Syntexis libocedrii (the cedar wood wasp). Binomial name Metasequoia glyptostroboides The Dawn Redwood (Metasequoia glyptostroboides) is a fast growing tree in the conifer family Cupressaceae native to the Sichuan-Hubei region of China. ... Families and Genera Glypheidae Glyphea Neoglyphea Mecochiridae Mecochirus Meyeria Pseudoglyphea Pemphicidae Pemphix The Glypheoidea (containing the glypheoid lobsters), is a group of lobster-like decapod crustaceans which forms an important part of fossil faunas, such as the Solnhofen limestone. ... Genera Archaeromma (extinct) Galloromma (extinct) Palaeomymar Mymarommatidae is a very small family of microscopic hymenopteran insects. ... Binomial name Sikhotealinia zhiltzovae Lafer, 1996 Wikispecies has information related to: Jurodidae The beetle family Jurodidae was originally described from fossils, but in 1996 a single species from the Russian Far East, described as Sikhotealinia zhiltzovae, was found and later was recognized to be a living representative of this otherwise... Binomial name Ginkgo biloba L. The Ginkgo (Ginkgo biloba), frequently misspelled as Gingko, and sometimes known as the Maidenhair Tree, is a unique tree with no close living relatives. ... Binomial name Syntexis libocedrii Rohwer, 1915 The Anaxyelidae is a wood wasp family within the Symphyta, containing only a single living species, Syntexis libocedrii, (also called the cedar wood wasp or incense-cedar wood wasp), though the family has an extensive Mesozoic fossil record; this species is thus a living...

Note that just because a living fossil is a surviving representative of an archaic lineage does not necessarily require that it retains all of the "primitive" features (plesiomorphies) of the lineage it is descended from; that is, they may possess one to many derived features (autapomorphies), that have evolved since the time of their lineage's divergence. All that is required is that they can be unambiguously assigned to an otherwise extinct lineage (rarely are they identical to the fossil forms). This cladogram shows the relationship among various insect groups. ... An autapomorphy in cladistics is a derived trait that is unique to a given taxon. ...

Note the similarity between the 170 million year old fossil Ginkgo sp. leaves on the left, and the living plant on the right. Photograph of fossil leaves from the plant Ginkgo taken by Dlloyd. ... Wikipedia does not have an article with this exact name. ...

Examples

Some of these are informally known as "living fossils".

Plants

• Ginkgo tree (Ginkgoaceae)
• Horsetails Equisetum (Equisetaceae)
• Metasequoia Dawn Redwood (Cupressaceae; a borderline example, related to Sequoia and Sequoiadendron)
• Sciadopitys tree (Sciadopityaceae)
• Whisk ferns Psilotum (Psilotaceae)
• Welwitschia
• Wollemia tree (Araucariaceae; a borderline example, related to Agathis and Araucaria)

Animals

• Vertebrates
  • Mammals
    • Cypriot mouse (Mus cypriacus)
    • Laotian Rock Rat (Laonastes aenigmamus)
    • Monotremes (the Platypus and echidnas)
    • Mountain Beaver (Aplodontia rufa)
  • Birds
    • Hoatzin (Ophisthocomus hoazin)
  • Reptiles
    • Crocodilia (Crocodiles, Gavials and Alligators)
    • Tuatara (Sphenodon punctatus and Sphenodon guntheri)
  • Fish
    • Coelacanth (Latimeria menadoensis and Latimeria chalumnae)
    • Queensland lungfish (Neoceratodus fosteri)
  • Sharks
    • Frilled shark (Chlamydoselachus anguineus)
  • Amphibians
    • Purple frog (Nasikabatrachus sahyadrensis)
• Invertebrates
  • Insects
    • Cedar wood wasp (Syntexis libocedrii)
    • Notiothauma reedi, a scorpionfly relative
    • Sikhotealinia zhiltzovae, a Jurodid beetle
    • Mymarommatid wasps (10 known species in genus Palaeomymar)
    • Parasitic wood wasps (about 70 species in 16 genera)
    • Peloridiid bugs (fewer than 30 species in 13 genera)
  • Crustaceans
    • Neoglyphea inopinata, N. neocaledonica, and Laurentaeglyphea neocaledonica ; three glypheoid lobsters
    • Triops cancriformis, a notostracid crustacean
  • Other invertebrates
    • Crinoids
    • Horseshoe crab (Limulus polyphemus)
    • Lingula anatina, an inarticulate brachiopod
    • Neopilina galateae, a monoplacophorid mollusc
    • Nut clam (Ennucula superba)
    • Onychophorans, for instance Peripatus

Binomial name Ginkgo biloba L. The Ginkgo (Ginkgo biloba), frequently misspelled as Gingko, and sometimes known as the Maidenhair Tree, is a unique tree with no close living relatives. ... Species The horsetails are vascular plants, comprising 15 species of plants in the genus Equisetum. ... Binomial name Metasequoia glyptostroboides Hu & Cheng Metasequoia glyptostroboides (Dawn Redwood) is a fast growing tree in the conifer family Cupressaceae native to the Sichuan-Hubei region of China. ... Binomial name Sequoia sempervirens (D. Don) Endl. ... Binomial name Sequoiadendron giganteum (Lindl. ... Binomial name Sciadopitys verticillata The Koyamaki (Sciadopitys verticillata) or Japanese Umbrella-pine, is a unique conifer endemic to Japan. ... Species Psilotum nudum (L.) Beauvois - Whisk Fern Psilotum complanatum Sw. ... Binomial name Welwitschia mirabilis Hook. ... Binomial name Wollemia nobilis W.G.Jones, K.D.Hill & J.M.Allen Wollemia nobilis is a remarkable coniferous tree that was discovered in 1994 in a remote series of narrow, steep-sided sandstone gorges in a mild temperate-zone rainforest wilderness area of the Wollemi National Park in New... Species See text The genus Agathis, commonly known as kauri or dammar forms a relatively small group of 21 species of evergreen trees in the family Araucariaceae, characteristically with very large trunks and little or no branching for some way up. ... Species See text. ... Binomial name Mus cypriacus Cucchi et al. ... Binomial name Laonastes aenigmamus Jenkins, Kilpatrick, Robinson, Timmins, 2005 The Laotian rock rat or kha-nyou (Laonastes aenigmamus), sometimes called the rat-squirrel, is a rodent species of the Khammouan region of Laos. ... Families †Kollikodontidae Ornithorhynchidae - Platypus Tachyglossidae - Echidnas †Steropodontidae Monotremes (monos, single + trema, hole; refers to the cloaca) are mammals that lay eggs instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). ... Binomial name Ornithorhynchus anatinus (Shaw, 1799) Platypus range (indicated by darker shading)[3] The Platypus (Ornithorhynchus anatinus) is a semi-aquatic mammal endemic to eastern Australia and Tasmania. ... Species Genus Tachyglossus    T. aculeatus Genus Zaglossus    Z. attenboroughi    Z. bruijnii    Z. bartoni    Z. hacketti (extinct)    Z. robustus (extinct) Echidnas, sometimes also referred to as spiny anteaters, are the only surviving monotremes apart from the Platypus. ... Binomial name Aplodontia rufa Richardson, 1829 The Mountain Beaver (Aplodontia rufa) is a rodent unrelated to beavers and that is not usually found in mountainous areas. ... Binomial name Ophisthocomus hoazin (Muller, 1776) The Hoatzin (Opisthocomus hoazin) is an odd species of tropical bird which is found in the swamps associated with the Amazon and Orinoco rivers of South America. ... Families Gavialidae Alligatoridae Crocodylidae Crocodilia is an order of large reptiles that appeared about 84 million years ago in the Late Cretaceous Period (Campanian stage). ... Genera Mecistops Crocodylus Osteolaemus See full taxonomy. ... Binomial name Gavialis gangeticus (Gmelin, 1789) Taxonomy The Gharial (Gavialis gangeticus) is the only surviving member of the family Gavialidae, a long-established group of crocodile-like reptiles with long, narrow jaws. ... Species Alligator mississippiensis Alligator sinensis An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. ... Species Sphenodon punctatus (Gray, 1842) Sphenodon guntheri Buller, 1877 Sphenodon diversum (extinct) The tuatara is a reptile of the family Sphenodontidae, endemic to New Zealand. ... Binomial name Sphenodon guntheri (Buller, 1877) The Brothers Island tuatara (Sphenodon guntheri) is a species of tuatara occurring naturally only on 4 hectare North Brother Island in The Brothers Islands in Cook Strait, New Zealand. ... This article or section does not cite its references or sources. ... Binomial name Neoceratodus forsteri Krefft, 1870 The Queensland Lungfish, also known as Burnett Salmon and Barramunda, is the sole member of the family Ceratodontidae, and one of the only six lungfish species that remain. ... Binomial name Chlamydoselachus anguineus Garman, 1884 The frilled shark, Chlamydoselachus anguineus, is a primitive shark species, of the family Chlamydoselachidae in the order Hexanchiformes. ... Binomial name Nasikabatrachus sahyadrensis Bijui, Bossuyt, 2003 Nasikabatrachus sahyadrensis is a frog species from the Western Ghats, India. ... Binomial name Syntexis libocedrii Rohwer, 1915 The Anaxyelidae is a wood wasp family within the Symphyta, containing only a single living species, Syntexis libocedrii, (also called the cedar wood wasp or incense-cedar wood wasp), though the family has an extensive Mesozoic fossil record; this species is thus a living... Binomial name Notiothauma reedi MacLachlan, 1877 The Mecopteran family Eomeropidae contains only a single living species, Notiothauma reedi, known from the Nothofagus forests in southern Chile. ... Binomial name Sikhotealinia zhiltzovae Lafer, 1996 Wikispecies has information related to: Jurodidae The beetle family Jurodidae was originally described from fossils, but in 1996 a single species from the Russian Far East, described as Sikhotealinia zhiltzovae, was found and later was recognized to be a living representative of this otherwise... Genera Archaeromma (extinct) Galloromma (extinct) Palaeomymar Mymarommatidae is a very small family of microscopic hymenopteran insects. ... Genera and species about 70 species in 16 genera The family Orussidae (the sole living member of the superfamily Orussoidea) is the only Symphytan group which is parasitic, thus giving them the common name parasitic wood wasps. ... Families Peloridiidae Coleorrhyncha is traditionally considered a suborder of Hemiptera, though there are alternative classifications in which it is treated as an infraorder within the suborder Prosorrhyncha, in which case it is called Peloridiomorpha (see the Heteroptera and Prosorrhyncha pages for a discussion). ... Families and Genera Glypheidae Glyphea Neoglyphea Mecochiridae Mecochirus Meyeria Pseudoglyphea Pemphicidae Pemphix The Glypheoidea (containing the glypheoid lobsters), is a group of lobster-like decapod crustaceans which forms an important part of fossil faunas, such as the Solnhofen limestone. ... Genera Lepidurus Triops Notostracans (often just called Triops, tadpole shrimp or shield shrimp) are small crustaceans, with internal compound eyes and a flattened shield covering the head and leg-bearing segments of the body. ... Genus Lepidurus Triops They grow up to 11cm in length. ... Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca The crustaceans (Crustacea) are a large group of arthropods, comprising approximately 52,000 described species [1], and are usually treated as a subphylum [2].They include various familiar animals... Orders Articulata Cladida(extinct) Flexibilia(extinct) Camerata(extinct) Disparida(extinct) Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the echinoderms (phylum Echinodermata). ... Binomial name Limulus polyphemus Linnaeus, 1758 The horseshoe crab (Limulus polyphemus) is a chelicerate arthropod, therefore it is more closely related to spiders and scorpions than crabs. ... Subphyla and classes See Classification Brachiopods (from Latin brachium, arm + New Latin -poda, foot) are a phylum of animals. ... Orders Cyrtonellida 1987 Tryblidiida 1987 [Tryblidioidea] Tryblidiida 1982 [Bellerophontida] 1987 Pelagiellida 1987 Monoplacophora is a class of Mollusks thought to be extinct until 1952, when a living animal was dredged up from deep marine sediments. ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia † Helcionelloida † ?Bellerophontidae The molluscs (British spelling) or mollusks (American spelling) are the large and diverse phylum Mollusca, which includes a variety of familiar animals well-known for their decorative shells or as seafood. ... Genera Peripatus . ...

History

The term was first coined by Charles Darwin in his The Origin of Species, when discussing Ornithorhynchus (the platypus) and Lepidosiren (the South American lungfish). On page 49, he wrote: Charles Robert Darwin (12 February 1809 – 19 April 1882) was an eminent English naturalist who achieved lasting fame by convincing the scientific community that species develop over time from a common origin. ... British naturalist Charles Darwins book, The Origin of Species, is one of the pivotal works in scientific literature and arguably the pre-eminent work in biology. ... This article is about the monotreme mammal. ... Binomial name Lepidosiren paradoxa The South American Lungfish (Lepidosiren paradoxa Fitzinger 1837) is the single species of lungfish found in swamps and slow-moving waters of South America. ...

"...All fresh-water basins, taken together, make a small area compared with that of the sea or of the land; and, consequently, the competition between fresh-water productions will have been less severe than elsewhere; new forms will have been more slowly formed, and old forms more slowly exterminated. And it is in fresh water that we find seven genera of Ganoid fishes, remnants of a once preponderant order: and in fresh water we find some of the most anomalous forms now known in the world, as the Ornithorhynchus and Lepidosiren, which, like fossils, connect to a certain extent orders now widely separated in the natural scale. These anomalous forms may almost be called living fossils; they have endured to the present day, from having inhabited a confined area, and from having thus been exposed to less severe competition."

Other definitions

There are quite a lot of (ambiguous) definitions denoting living fossils:

• A living species that lived through a large portion of geologic time

To prove this, all living specimens must belong to the same fossil species. This rules out Limulus, Peripatus, Latimeria, Sphenodon, Didelphis, the platypus, and many others. To allow some flexibility, the genus could be used. Paleontological taxonomy relies on hard-part morphology (the paleontological species concept), so there is a bias towards longer species turnover times, and relationships can only be inferred partially. Modern molecular biology has shown that genetic rates of change are relatively uniform and not well related to morphological change rates. So from a more molecular basis of interbreeding capabilities there are essentially no such thing as species that lived through a long geological time. However, with the proviso that we are using the special case of a paleontological species name, the definition does hold together in context.

• A living species morphologically and/or physiologically resembling a fossil species through a large portion of geologic time (morphological stasis)

The living specimens need not belong to the same fossil species (or even genus). There must at least be some physiological resemblance.

The coelacanth for example, is a marine fish. The Mesozoic coelacanth species lived in salt and fresh water. Osmoregulation in Latimeria is handled by ureum retention. Ureum retention is considered to be an indication of fresh water ancestry. This means that the coelacanth lineage has evolved from freshwater to saltwater.

The resemblance between Peripatus and Aysheaia (an early Cambrian animal from the Burgess Shale) is striking (as of now, both are classified in the Tardipolypoda (Tardigrada and Onychophora), were it not that Aysheaia was a marine animal, while Peripatus lives in tropical leaf mould.

• A living species/clade with many primitive characteristics

This is a more neutral definition. However, it does not make it clear whether the taxon is truly old, or it simply has many plesiomorphies. Note that, as mentioned above, the converse may hold for true living fossil taxa; that is, they may possess a great many derived features (autapomorphies), and not be particularly "primitive" in appearance.

• Any one of the above three definitions, but also with a relict distribution in refuges.

Some paleontologists consider "living fossils" with large distributions (such as Triops cancriformis) not to be real living fossils. In the case of Triops cancriformis (living from the Triassic until now), the Triassic specimens have lost most of their appendages (mostly only carapaces remain), and they haven't been thoroughly examined since 1938.

• Any of the first three definitions, but the clade also has a low taxonomic diversity (low diversity lineages)

An organism's living fossil status can be rejected if the (smallest) clade the species belongs to is species rich, as this would imply (recent) speciation.

The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... Look up taxonomy in Wiktionary, the free dictionary. ... The term morphology in biology refers to the outward appearance (shape, structure, colour, pattern) of an organism or taxon and its component parts. ... In biology, a species is the basic unit of biodiversity. ... The term morphology in biology refers to the outward appearance (shape, structure, colour, pattern) of an organism or taxon and its component parts. ... Leonardo da Vincis Vitruvian Man, an important early achievement in the study of physiology. ... The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. ... Osmoregulation is the active regulation of the osmotic pressure of bodily fluids to maintain the homeostasis of the bodys water content; that is it keeps the bodys fluids from becoming too dilute or too concentrated. ... Aysheaia pedunculata is a soft-bodied, caterpillar-shaped organism average body length of 1-6 cm. ... The Cambrian is a major division of the geologic timescale that begins about 542 ± 1. ... Hallucigenia sparsa, one of the organisms unique to the Burgess Shale. ... Classes Heterotardigrada Mesotardigrada Eutardigrada Tardigrades (Tardigrada), or water bears, are a phylum of small, segmented animals, similar and related to the Arthropods. ... An autapomorphy in cladistics is a derived trait that is unique to a given taxon. ... The term relict is used to refer to surviving remnants of natural phenomena. ... Look up refuge in Wiktionary, the free dictionary. ... The Triassic is a geologic period that extends from about 251 to 200 Ma (million years ago). ... The term carapace refers to a dorsal section of an exoskeleton or shell, in a number of animal groups. ... Year 1938 (MCMXXXVIII) was a common year starting on Saturday (link will take you to calendar). ...

External links

• Scientists find lamprey a 'living fossil'