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Ichthyostegalia is an order of extinct amphibians, representing the earliest landliving vertebrates. The group is thus an evolutionary grade rather than a clade . [ 1 ] While the group are recognized as having feet rather than fins, most, if not all, had internal gills in adulthood and lived primarily as shallow water fish and spent minimal ...
Traditionally, Ichthyostega was considered part of an order named for it, the "Ichthyostegalia". However, this group represents a paraphyletic grade of primitive stem-tetrapods and is not used by many modern researchers. Phylogenetic analysis has shown Ichthyostega is intermediate between other primitive stegocephalian stem-tetrapods. The ...
These labyrinthodonts are often grouped together as the order Ichthyostegalia, though the group is an evolutionary grade rather than a clade. [24] Ichthyostegalians were predominantly aquatic and most show evidence of functional internal gills throughout life, and probably only occasionally ventured onto land.
The precise definition of "tetrapod" is a subject of strong debate among paleontologists who work with the earliest members of the group. ... Subclass Ichthyostegalia ...
Ichthyostegalia, the primarily aquatic primitive labyrinthodonts such as Acanthostega, Ichthyostega, Tulerpeton, and probably loxommatids. [ 1 ] Both Ichthyostegalia and Labyrinthodontia constitute paraphyletic evolutionary grades rather than clades, with amniotes and modern amphibians branching off at some point from the latter.
Hynerpeton (/ h aɪ ˈ n ɜːr p ə t ɒ n / lit. ' creeping animal from Hyner ') is an extinct genus of early four-limbed vertebrate that lived in the rivers and ponds of Pennsylvania during the Late Devonian period, around 365 to 363 million years ago.
Genus [2] Status Age [2] Location [2] Description Images Acanthostega. Valid Famennian: Greenland: 0.6 m long Densignathus. Valid Famennian: United States: Elginerpeton
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