| Tetrapodomorpha | |
|---|---|
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| Life restoration ofPanderichthys | |
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| Moderntetrapods | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Rhipidistia |
| Clade: | Tetrapodomorpha Ahlberg, 1991 |
| Subgroups | |
See alsobelow. | |
| Synonyms | |
Choanata | |
Tetrapodomorpha (also known asChoanata[3]) is aclade ofvertebrates consisting oftetrapods (four-limbed vertebrates) and their closestsarcopterygian relatives that are more closely related to living tetrapods than to livinglungfish. Advanced forms transitional between fish and the earlylabyrinthodonts, such asTiktaalik, have been referred to as "fishapods" by their discoverers, being half-fish, half-tetrapods, in appearance and limb morphology. The Tetrapodomorpha contains thecrown group tetrapods (the last common ancestor of living tetrapods and all of its descendants) and several groups of earlystem tetrapods, which includes several groups of related lobe-finned fishes, collectively known as theosteolepiforms. The Tetrapodomorpha minus thecrown group Tetrapoda are thestem Tetrapoda, aparaphyletic unit encompassing the fish to tetrapod transition.
Among the characteristics defining tetrapodomorphs are modifications to the fins, notably ahumerus with convex head articulating with the glenoid fossa (the socket of theshoulder joint). Another key trait is the internal nostril orchoana. Most fish have two pairs of nostrils, one on either side of the head for incoming water (incurrent nostrils) and another pair for outgoing water (excurrent nostrils). In early tetrapodomorphs likeKenichthys, the excurrent nostrils had shifted towards the mouth's perimeter. In later tetrapodomorphs, including tetrapods, the excurrent nostril is positioned inside the mouth, where it is known as thechoana.[4] The nearly-equivalent clade Choanata often refers to these later forms specifically.[2]
Tetrapodomorph fossils are known from the earlyDevonian onwards, and includeOsteolepis,Panderichthys,Kenichthys andTungsenia.[1] Tetrapodomorpha evolved from ancientlobe-finned fish (sarcopterygians) around390 million years ago in theMiddle Devonian period.[5]
After Benton, 2004;[7] and Swartz, 2012.[8]
Other clades include theEotetrapodiformes (Tinirau,Platycephalichthys, theTristichopteridae andElpistostegalia).[8] Older taxa which include latestem tetrapods and earlytetrapods are theLabyrinthodontia andIchthyostegalia.
The cladogram is based on a phylogenetic analysis of 46 taxa using 204 characters by B. Swartz in 2012.[8]
| Tetrapodomorpha | |
The following cladogram follows the results found by Clementet al. (2021).[9]
| Tetrapodomorpha | |
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