Porolepiformes

Porolepiforms Temporal range: 416–318  Ma PreꞒ Ꞓ O S D C P T J K Pg N Devonian and Carboniferous
Various genera
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Sarcopterygii
Clade:	Rhipidistia
Clade:	Dipnomorpha
Order:	† Porolepiformes Jarvik 1942
Genera
†Porolepidae † Heimenia ØRvik 1969 † Porolepis †Holoptychiidae Owen 1860 ?† Duffichthys Ahlberg 1992 ?† Ventalepis Schultze 1980 † Pseudosauripterus † Glyptolepis † Holoptychius † Laccognathus

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]

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]

†Porolepidae † Heimenia ensis ØRvik 1969 † Porolepis † P. brevis Jarvik 1937 † P. elongata Jarvik 1937 † P. posnaniensis (Kade 1858) † P. siegenensis Gross 1935 † P. spitsbergensis Jarvik 1937 †Holoptychidae ?† Ventalepis ketleriensis Schultze 1980 ?† Duffichthys mirabilis Ahlberg 1992 † Pseudosauripterus anglicus (Woodward 1891) † Glyptolepis † G. baltica † G. groenlandica Jarvik 1972 † G. leptopterus Agassiz 1844 † G. paucidens † Holoptychius † H. americanus Leidy 1843 † H. flemingi Agassiz 1844 † H. giganteus Agassiz 1839 † H. halli Newberry 1889 † H. hopkinsii M'Coy 1844 † H. nobilissimus Agassiz 1835 † H. quebecensis † Laccognathus † L. panderi TGross 1941 † L. grossi Vorobyeva 2006 † L. embryi Downs et al. 2011

References

1. Nelson, Joseph S. (16 March 2016). Fishes of the World. ISBN   978-1-119-22081-7. OCLC   951128215.
2. Jarvik, Erik. 1980. Basic structure and evolution of vertebrates. Vol. 1–2. Academic Press (London).
3. Schultze, Hans-Peter & Trueb, Linda (1991). Origins of the higher groups of tetrapods: controversy and consensus. Cornell University Press. p. 37. ISBN   978-0-8014-2497-7.
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.
6. Vorobyeva, E.I. (2006). "A new species of Laccognathus (Porolepiform Crossopterygii) from the Devonian of Latvia". Paleontol. J. 40 (3). Physorg.com: 312–322. doi:10.1134/S0031030106030129. S2CID   129696592.
7. Haaramo, Mikko (2003). "Porolepiformes". In Mikko's Phylogeny Archive. Retrieved November 4, 2013.

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