Rhipidistia

Source: Wikipedia, the free encyclopedia.

Rhipidistians
Temporal range:
Ma
LungfishMammalReptileTiktaalikAmphibianBird
Diversity of Rhipidistia
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sarcopterygii
Clade: Rhipidistia
Subgroups

Rhipidistia, also known as Dipnotetrapodomorpha,

lungfishes
.

Rhipidistia includes Porolepiformes and Dipnoi. Extensive fossilization of lungfishes has contributed to many evolutionary studies of this group. Evolution of autostylic jaw suspension, in which the palatoquadrate bone fuses to the cranium, and the

birds), are unique to this group. Another feature shared by lungfish and tetrapods is the divided atrium.[3]

The precise time at which the choana of tetrapods evolved is debated, with some considering early rhipidistians as the first choanates. The feature is also present in modern lungfish but is probably a case of convergent evolution. The basal stem-lungfish Diabolepis did not possess it. Instead, it had four nostrils (two anterior and two posterior) like most fish. However, its posterior nares are very close to the lip, meaning a ventral 'displacement' of the posterior nostril can be considered a synapomorphy of the lungfish-tetrapod clade. The complete choana then seems to have developed independently in the two surviving clades.[4]

Etymology

The word "Rhipidistia" is from

romanized: rhipídion, lit. 'small bellows
'.

The word "Dipnotetrapodomorpha" is from

combining form
of the numeral τέτταρες (tettares); from Ancient Greek: -ποδ-, romanized: -pod-, the combining form of πούς (pous) meaning "foot"; and from Ancient Greek: -μορϕος, romanized: -morphos, the combining form of μορϕή (morph) meaning "physical shape".

Relationships

The cladogram presented below is based on studies compiled by Philippe Janvier and others for the Tree of Life Web Project,[5] and Swartz 2012.[6]

Sarcopterygii

†

Onychodontidae

Actinistia
(coelacanths)

Rhipidistia

†Styloichthys

Dipnomorpha

†Porolepiformes

Dipnoi
(lungfishes)

Tetrapodomorpha

References

  1. ISBN 978-0-471-75644-6
    . Retrieved 9 May 2015.
  2. ^ "Encyclopædia Britannica". Retrieved 3 April 2014.
  3. OCLC 1022979490
    .
  4. S2CID 4422813
    .
  5. ^ Janvier, Philippe. 1997. Vertebrata. Animals with backbones. Version 01 January 1997 (under construction). http://tolweb.org/Vertebrata/14829/1997.01.01 in The Tree of Life Web Project, http://tolweb.org/
  6. PMID 22448265
    .

External links
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