Tetrapodomorpha


Tetrapodomorpha

Taxobox
name = Tetrapodomorphs
fossil_range = late Early Devonian - Recent



image_width = 200px
image_caption = The basal tetrapodomorph "Tiktaalik".
regnum = Animalia
phylum = Chordata
subphylum = Vertebrata
classis = Sarcopterygii
subclassis = Tetrapodomorpha
subclassis_authority = Ahlberg, 1991
subdivision_ranks = Subgroups
subdivision =
* See text
" – exhibited a sequence of adaptations:
  • "Panderichthys", suited to muddy shallows;
  • "Tiktaalik" with limb-like fins that could take it onto land;
  • Early tetrapods in weed-filled swamps, such as:
    • "Acanthostega" which had feet with eight digits,
    • "Ichthyostega" with limbs.
Descendants also included pelagic lobe-finned fish such as coelacanth species.]

Tetrapodomorpha is a clade of vertebrates, consisting of sarcopterygians with a number of features of tetrapods. Primitive forms, like "Tiktaalik", have been referred to as "fishapods" by their discoverers, since they were half-fish half-tetrapods, at least in appearance.

Tetrapodomorpha contains the true tetrapods and several groups of related lobe-finned fishes, collectively known as the osteolepiforms.

Among the characters defining the tetrapodomorphs are modifications to the fins, notably a humerus with convex head articulating with the glenoid fossa (the socket of the shoulder joint).

Tetrapodomorph fossils are known from the early Devonian onwards, and include "Osteolepis" and "Panderichthys".

Taxonomy and phylogeny

* Class Sarcopterygii
** Subclass Tetrapodomorpha
*** "Kenichthys"
*** Order Rhizodontida
*** Superorder Osteolepidida (or Osteolepiformes)
**** Family Osteolepididae
***** "Osteolepis"
**** Family Tristichopteridae
***** "Eusthenopteron"
**** Family Megalichthyidae
***** "Megalichthys"
**** Family Canowindridae
**** (unranked) Elpistostegalia
***** Order Panderichthyida
***** "Tiktaalik"
***** "Livoniana"
***** "Metaxygnathus"
***** "Ventastega"
***** Superclass Tetrapoda

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* After Benton, 2004 [http://palaeo.gly.bris.ac.uk/benton/vertclass.html] :

References

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