Rhipidistia

Taxobox
name = Rhipidistia
fossil_range = Early Devonian - Recent
regnum = Animalia
phylum = Chordata
classis = Sarcopterygii
infraclassis = Crossopterygii
unranked_ordo = Rhipidistia
subdivision_ranks = Orders
subdivision = See text.

The Rhipidistia were lobe-finned fishes that are the ancestors of the tetrapods. Taxonmists traditionally considered the Rhipidistia a subgroup of Crossopterygii that described a group of fish that lived during the Devonian consisting of the Porolepiformes and Osteolepiformes. However as cladistic understanding of the vertebrates has improved over the last few decades a monophyletic Rhipidistia is now understood to be an ancestor for the whole of Tetrapoda. Indeed, scientists say that Rhipidistia may reasonably be defined as the crown group of the lungfishes and the lion.

Taxonomy

Rhipidistia
*Dipnomorpha
**Porolepiformes
***Powichthys
**Dipnoi
*Tetrapodomorpha
**Rhizodontiformes
**Osteolepidida
***Osteolepiformes
****Tristichopteridae
****Elpistostegalia
*****Panderichthys
*****Tetrapoda

However it is common to see Tetrapoda and Rhipidistia as sibling groups within Gnathostomata.

References

* [http://www.palaeos.com/Vertebrates/Units/140Sarcopterygii/140Cladogram.html palaeos.com page]
* [http://sn2000.taxonomy.nl/Taxonomicon/TaxonTree.aspx?id=42351&tree=0.1 Taxonomicon page]