page_title: Lungfish
section_title: Taxonomy
hierarchical_section_title: Lungfish / Taxonomy
caption_attribution_description: Ceratodus
context_page_description: Lungfish are freshwater rhipidistian fish belonging to the subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton.
  Today there are only six known species of lungfish, living only in Africa, South America, and Australia. The fossil record shows that lungfish were abundant since the Triassic. While vicariance would suggest this represents an ancient distribution limited to the Mesozoic supercontinent Gondwana, the fossil record suggests advanced lungfish had a widespread freshwater distribution and the current distribution of modern lungfish species reflects extinction of many lineages subsequent to the breakup of Pangaea, Gondwana and Laurasia. Lungfish have historically been referred to as salamanderfish, but this term more often refers to Lepidogalaxias salamandroides.
context_section_description: The relationship of lungfishes to the rest of the bony fish is well understood:
  Lungfishes are most closely related to Powichthys, and then to the Porolepiformes.
  Together, these taxa form the Dipnomorpha, the sister group to the Tetrapodomorpha.
  Together, these form the Rhipidistia, the sister group to the Coelacanths.
  Recent molecular genetic analyses strongly support a sister relationship of lungfishes and tetrapods (Rhipidistia), with Coelacanths branching slightly earlier.
  The relationships among lungfishes are significantly more difficult to resolve.  While Devonian lungfish had enough bone in the skull to determine relationships, post-Devonian lungfish are represented entirely by skull roofs and teeth, as the rest of the skull is cartilaginous.  Additionally, many of the taxa already identified may not be monophyletic.
  Current phylogenetic studies support the following relationships of major lungfish taxa: Class Osteichthyes, subclass Sarcopterygii, order Dipnoi.
caption: Illustration of Ceratodus by Heinrich Harder
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