Porolepiformes

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Porolepiformes is an order of prehistoric lobe-finned fish which lived during the Devonian period (about 416 to 359 million years ago). They are thought to represent the sister group to lungfish (class Dipnoi).[1] The group contains two families: Holoptychiidae and Porolepididae.

Porolepiformes was established by the Swedish paleontologist Erik Jarvik, and were thought to have given rise to the salamanders and caecilians independently of the other tetrapods.[2] He based this conclusion on the shapes of the snouts of the aforementioned groups. This view is no longer in favour in Paleontology.[3]

Jarvik also claimed the existence of choanae in porolepiformes which linked them to tetrapods, but this has remained controversial.[4] Recent phylogenetic reconstruction places porolepiformes close to lungfishes.[5]

More recent evidence has shown that at least one genus Laccognathus was most likely amphibious.[6]

File:Holoptychius quebecensis -"salamanderfisk".jpg
Porolepiform fossil (cast) from a Swedish natural history museum. Note that the description calls it a "Salamander fish", in accordance with Jarvik's obsolete hypothesis.

Phylogeny

Mikko's Phylogeny Archive:[7]

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References

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  2. Jarvik, Erik. 1980. Basic structure and evolution of vertebrates. Vol. 1–2. Academic Press (London).
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  4. Clement, G., 2001. Evidence for lack of choanae in the Porolepiformes. Journal of Vertebrate Paleontology, 21: 795–802.
  5. Janvier , P., Early vertebrates. Oxford science publications. 1996, Oxford, New York: Clarendon Press; Oxford University Press.
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