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Although the Trilobita went entirely extinct
at the end of the Permian (251 million
years ago [mya]), when >90% of all species on the planet were extinguished,
the pattern of decline for trilobites had been significant since the end
of the Ordovocian. By the end of the Devonian (359 mya), the last
of the Phacopidae went extinct, ending the order Phacopida. All of the
orders of trilobites had gone extinct, except for one: the Proetida. This order persisted
into the Carboniferous (with two superfamilies represented: Aulacopleuroidea and
Proetoidea. There
was even a major adaptive radiation among the family Phillipsiidae (especially
various subfamilies such as Phillipsiinae and Ditomopyginae) in the early
Carboniferous, as changes in the world's continents created expanding habitat
opportunities. But the number of taxa fell dramatically after the Mid-Carboniferous,
and by the start of the Permian (299 mya), only the families Brachymetopidae, Phillipsiidae,
and Proetidae remained. The table below lists all of the trilobite genera
that existed in the Permian, and indicates when these genera became extinct.
|
| Superfamily |
Family |
Subfamily |
Genus |
Extinction |
| Aulacopleuroidea |
Brachymetopidae |
Brachymetopinae |
Cheiropyge |
End Permian |
| Brachymetopus |
Early Permian |
|||
| Proetoidea |
Proetidae* |
Proetinae |
Neogriffithides |
Middle Permian |
| Anujaspis |
Early Permian |
|||
| Phillipsiidae* |
Archegoninae |
Hildaphillipsia |
Middle Permian |
|
| Bollandiinae |
Kathwaia |
End Permian |
||
| Neoproetus |
Middle Permian |
|||
| Cummingellinae |
Bedicella |
Early Permian |
||
| Cummingella |
Early Permian |
|||
| Paraphillipsia |
End Permian |
|||
| Ditomopyginae |
Acanthophillipsia |
Middle Permian |
||
| Acropyge |
End Permian |
|||
| Ameura |
Early Permian |
|||
| Ampulliglabella |
Middle Permian |
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| Anisopyge |
Middle Permian |
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| Delaria |
Middle Permian |
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| Ditomopyge |
Late Permian |
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| Hentigia |
Early Permian |
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| Iranaspidion |
Late Permian |
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| Jimbokranion |
Middle Permian |
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| Microphillipsia |
Middle Permian |
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| Novoameura |
Early Permian |
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| Permoproetus |
Middle Permian |
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| Pseudophillipsia |
End Permian |
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| Timoraspis |
Middle Permian |
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| Triproetus |
Middle Permian |
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| Weaniinae |
Doublatia |
Early Permian |
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| Endops |
Middle Permian |
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| Nipponaspis |
Middle Permian |
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| Weania |
Early Permian |
The Last Trilobites
Owens (2003) reviewed the last trilobites to go extinct during the Permian, and revealed that five genera of trilobites persisted until the great extinction crisis at the end of the Permian. This event was perhaps the largest extinction event in Earth's history, wherein >90% of all species were extinguished. However, the fossil record reveals that for trilobites, there were two crises during the Permian, one during the Middle Permian (266 million years ago, in the Late Guadalupian Epoch), in which over half of the trilobite genera extant at the time were lost (see the numerous "Middle Permian" extinctions in the table above). Of those that remained, only five persisted to the end Permian event: Cheiropyge (an aulacopleuroid in the family Brachymetopidae), Kathwaia (a proetoid in the family Phillipsiidae, subfamily Bollandiinae), Paraphillipsia (Phillipsiidae, Cummingellinae), Acropyge (Phillipsiidae, Ditomopyginae), and Pseudophillipsia (also Ditomopyginae). Specimens of these genera are shown at right: These are the last genera of the trilobites, and are found in various localities today including Pakistan, China, Russia, Hungary, and Japan.Reconstructions of three of these Permian trilobite species are presented at bottom right: Leftmost: Cheiropyge koizumii (Japan, Brachymetopidae); Middle: Pseudophillipsia sumatrensis (Malaysia, Proetidae); Far right: Paraphillipsia karpinskyii (Ukraine, Proetidae) |
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Owens, R.M. 2003. The stratigraphical distribution and extinctions of Permian trilobites. Special Papers in Palaeontology 70:377-97.
