Ceratodontiformes

Ceratodontiformes is the only extant order of lungfish, containing the families Neoceratodontidae, Lepidosirenidae, and Protopteridae as well as many other extinct groups. Members of this group are the only lungfish known to have survived the Permian-Triassic extinction event.[1][2]

Ceratodontiformes
Temporal range:
Neoceratodus forsteri, a neoceratodontid
Lepidosiren paradoxa, a lepidosirenid
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Rhipidistia
Clade: Dipnomorpha
Class: Dipnoi
Order: Ceratodontiformes
Berg, 1940
Type genus
†Ceratodus
Agassiz, 1837
Families

Several extinct, see text

Synonyms
  • Lepidosireniformes L. S. Berg (No date given, per Fowler, 1947)

All lungfish of the order can and often do estivate (except the spotted African lungfish, which can but rarely does so).[3] All members of the order are obligatory air-breathers; only the Australian lungfish has functioning gills when adult; members of the Lepidosirenidae have gills only when they are larvae.[3] The lungfish also all have generally small scales and two lungs as opposed to the Australian lungfish's single lung.[3]

Taxonomy

The suborder was formerly defined as being within the order Ceratodontiformes and including the families Neoceratodontidae and Ceratodontidae, as they were formerly thought to be closely related to one another. However, phylogenetic analyses indicate that this classification is paraphyletic, as Ceratodontidae was found to be a sister group to a clade containing Lepidosirenidae, which was formerly classified as Lepidosireniformes, a distinct order from Ceratodontiformes. Due to this, Lepidosireniformes and Ceratodontiformes were redefined as families within the order Ceratodontiformes, redefined as including all lungfish more closely allied with Neoceratodontidae and Lepidosirenidae.[1]

The current taxa within the suborder are listed below, taxonomy based on Kemp et al (2017):

Ceratodontoidei

†Paraceratodus

†Ferganoceratodus

Neoceratodontidae

Lepidosirenidae

Protopteridae

†Gnathorhizidae

†Ptychoceratodontidae

†Ceratodontidae

The oldest fossils of the Ceratodontiformes are of Gnathorhizidae from the Late Carboniferous, which are thought to be closely related to modern Lepidosirenidae and Protopteridae. This would indicate that the order itself originated slightly earlier in the late Carboniferous and rapidly diversified into the multiple families between then and the start of the Permian, leading to a very deep split between the Neoceratodontidae and the Lepidosirenidae + Protopteridae.[1][4]

References
  1. Kemp, Anne; Cavin, Lionel; Guinot, Guillaume (2017-04-01). "Evolutionary history of lungfishes with a new phylogeny of post-Devonian genera". Palaeogeography, Palaeoclimatology, Palaeoecology. 471: 209–219. doi:10.1016/j.palaeo.2016.12.051. ISSN 0031-0182.
  2. "Fossilworks: Ceratodontoidei". fossilworks.org. Retrieved 17 December 2021.
  3. Kemp, Anne; Cavin, Lionel; Guinot, Guillaume (2017-04-01). "Evolutionary history of lungfishes with a new phylogeny of post-Devonian genera". Palaeogeography, Palaeoclimatology, Palaeoecology. 471: 209–219. Bibcode:2017PPP...471..209K. doi:10.1016/j.palaeo.2016.12.051. ISSN 0031-0182.
  4. "Fossilworks: Gnathorhizidae". fossilworks.org. Retrieved 17 December 2021.
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