Living fossil is an informal term for any living species which appears similar to a species otherwise only known from fossils and which has no close living relatives, or a group of organisms which have long fossil records.[1] Such groups have often survived major extinction events, and generally retain low taxonomic diversities.
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There are several competing and often ambiguous definitions of the term "living fossil". One definition holds that a "living fossil" is any living taxon morphologically and/or physiologically resembling a fossil species through a large portion of geologic time (morphological stasis).[2]
The term was coined by Charles Darwin in his On the Origin of Species, when discussing Ornithorhynchus (the platypus) and Lepidosiren (the South American lungfish):
| “ | ... 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. | ” |
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— Charles Darwin , On the Origin of Species, p49
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