Tetrapodomorpha

Tetrapodomorpha
Temporal range:
Early DevonianPresent, 409–0 Ma
The advanced tetrapodomorph Tiktaalik
Modern tetrapods
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sarcopterygii
Clade: Rhipidistia
Clade: Tetrapodomorpha
Ahlberg, 1991
Subgroups

See also below.

The Tetrapodomorpha (also known as Choanata) are a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advanced forms transitional between fish and the early labyrinthodonts, such as Tiktaalik, have been referred to as "fishapods" by their discoverers, being half-fish, half-tetrapods, in appearance and limb morphology. The Tetrapodomorpha contains the crown group tetrapods (the last common ancestor of living tetrapods and all of its descendants) and several groups of early stem tetrapods, which includes several groups of related lobe-finned fishes, collectively known as the osteolepiforms. The Tetrapodomorpha minus the crown group Tetrapoda are the stem Tetrapoda, a paraphyletic unit encompassing the fish to tetrapod transition.

Among the characteristics defining tetrapodomorphs are modifications to the fins, notably a humerus with convex head articulating with the glenoid fossa (the socket of the shoulder joint). Another key trait is the internal nostril or choana. 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 like Kenichthys, 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 the choana. The nearly-equivalent clade Choanata often refers to these later forms specifically.

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

Classification

In Late Devonian vertebrate speciation, descendants of pelagic lobe-finned fish.
The exact shape of the phylogenetic tree is uncertain with Zachelmie tetrapod tracks predating most tetrapodomorph fossils

Taxonomy

After Benton, 2004; and Swartz, 2012.

  • Infraclass Tetrapodomorpha

Other clades include the Eotetrapodiformes (Tinirau, Platycephalichthys, the Tristichopteridae and Elpistostegalia). Older taxa which include late stem tetrapods and early tetrapods are the Labyrinthodontia and Ichthyostegalia.

Relationships

The cladogram is based on a phylogenetic analysis of 46 taxa using 204 characters by B. Swartz in 2012.

Tetrapodomorpha 

Kenichthys

Rhizodontidae

Marsdenichthys

Canowindra

Koharalepis

Beelarongia

Gogonasus

Gyroptychius

Osteolepis

Medoevia

Megalichthyidae

Eotetrapodiformes

Spodichthys

Tristichopterus

Eusthenopteron

Jarvikina

Cabonnichthys

Mandageria

Eusthenodon

Tinirau

Platycephalichthys

Elpistostegalia

Panderichthys

Tiktaalik

Elpistostege

Elginerpeton

Ventastega

Acanthostega

Ichthyostega

Whatcheeriidae

Colosteidae

Crassigyrinus

Baphetidae

Tetrapoda (crown group)

The following cladogram follows the results found by Clement et al. (2021).

Dipnomorpha

Tetrapodomorpha

Kenichthys

Tungsenia

Rhizodontida

Hongyu

Gooloogongia

Sauripterus

Barameda

Screbinodus

Rhizodus

Strepsodus

Osteolepidida

Gyroptychius

Osteolepis

Gogonasus

Medoevia

Megalichthyidae

Canowindridae

Beelarongia

Canowindra

Koharalepis

Marsdenichthys

Spodichthys

Tristichopterus

Eusthenopteron

Jarvikina

Cabonnichthys

Platycephalichthys

Mandageria

Eusthenodon

Tinirau

Bruehnopteron

Panderichthys

Tiktaalik

Elpistostege

Tetrapoda

Ventastega

Acanthostega

Ichthyostega

Tulerpeton


This page was last updated at 2024-02-08 04:48 UTC. Update now. View original page.

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