Pseudoextinction

Pseudoextinction (or phyletic extinction) of a species occurs where there are no more living members of that species, but members of a daughter species or subspecies remain alive. As all species must have an ancestor of a previous species, much of evolution is believed to occur through pseudoextinction. However, it is difficult to prove that any particular fossil species is pseudoextinct unless genetic information has been preserved. For example, it is sometimes claimed that the extinct Hyracotherium (an ancient horse-like animal commonly known as an eohippus) is pseudoextinct, rather than extinct, because several species of horse, including the zebra and the donkey, are extant today. However, it is not known, and probably cannot be known, whether modern horses actually descend from members of the genus Hyracotherium, or whether they simply share a common ancestor.

Pseudotermination is extreme form of pseudoextinction, when lineage may continue in form of new species of frequently difficult to predict phylogeny.^[1]

Extirpation or regional disappearance is the stage in pseudoextinction, when progressive diachronous range contraction, may lead to, final extinction by the elimination of the last refuge, or population growth from this temporal bottleneck.^[1]

Pseudoextinction can sometimes apply to wider taxons than the species level. For instance, the entire Superorder Dinosauria is believed to have become pseudoextinct by many paleontologists, who argue that the feathered dinosaurs are the ancestors of modern day birds. Pseudoextinction for taxa higher than the genus level is easier to prove.

See also

• Main articles: on Extinction, and the Cretaceous-Tertiary extinction event
• Human extinction

References

1. ^ ^{a b} Westermann, Gerd E.G. (2001). "Modes of e×tinction, pseudo-e×tinction and distribution in Middle Jurassic ammonites: terminology". Canadian Journal of Earth Sciences 38: 187. doi:10.1139/cjes-38-2-187. 

External links

• The difficulty of differentiating extinction from pseudoextinction in the fossil record
• The Extinction Website
• The Extinction Forum, part of The Extinction Website.

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