Sarcopterygii

Encyclopedia : S : SA : SAR : Sarcopterygii

Sarcopterygii (from Greek sarx, flesh, and pteryx, fin) is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. These are bony fish with paired rounded fins. These fins, being similar to limbs, suggest that these fish may be ancestors of land vertebrates.

Most taxonomists who subscribe to the cladistic approach include within this group the superclass Tetrapoda, which in turns consists of all species of four-limbed vertebrates. The fin-limbs of sarcopterygiians show such a strong similarity to the expected ancestral form of tetrapod limbs that they have been universally considered the direct ancestors of tetrapods in the scientific literature.

Taxonomy and Phylogeny

• Class SARCOPTERYGII
• * Subclass Coelacanthimorpha
• ** Order Coelacanthiformes
• * Rhipidistia
• **Subclass Dipnoi
• *** Order Ceratodontimorpha
• **Subclass Tetrapodomorpha
• *** Order Rhizodontida
• *** Superorder Osteolepidida
• **** Family Tristichopteridae
• ***** Eusthenopteron
• ***** Hyneria
• **** Order Osteolepiformes
• *** Order Panderichthyida
• ***Tiktaalik
• *** Tetrapoda

Late Devonian vertebrate speciation saw lobe-finned fish like Panderichthys having descendants such as Eusthenopteron which could breathe air in muddy shallows, then Tiktaalik whose limb-like fins could take it onto land, preceding the first tetrapod amphibians such as Acanthostega whose feet had eight digits, and Ichthyostega with developed limbs, negotiating weed-filled swamps. Lobe-finned fish evolved into Coelacanth species which survive to this day.

This level of taxonomy is in flux however; the membership of Sarcopterygii is likely to change, and it may even be discontinued as a classification.

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.