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The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.
In effect, "tetrapod" is a name reserved solely for animals which lie among living tetrapods, so-called crown tetrapods. This is a node-based clade , a group with a common ancestry descended from a single "node" (the node being the nearest common ancestor of living species).
Colosteus is an extinct genus of colosteid tetrapod from the Late Carboniferous (late Westphalian stage) of Ohio.Its remains have been found at the Linton site in Saline Township, Ohio, where it is one of the most common tetrapods, [1] and at the Five Points site in Mahoning County, Ohio. [2]
In the tetrapod and higher clades from the lower-middle Famennian there are several defining changes on the basis of anatomy of Ichthyostega, Tulerpeton, and Acanthostega. In the cranium, there is a stapes derived from the hyomandibular of fishes; a single bilateral pair of nasal bones, and a fenestra ovalis in the otic capsule of the braincase ...
That means tetrapods may have thrived in colder climates earlier than scientists expected, prompting more questions about how and when they took over the Earth. “The early story of the first tetrapods is much more complex than we thought,” said co-author Claudia Marsicano at the University of Buenos Aires, who was part of the research.
Nine tetrapod trackways from three sites have been reported from the Valentia Slate Formation of Valentia Island, Ireland. [2] [3] The Valentia Slate Formation is composed mostly of purple coloured fine-grained sandstones and siltstones interpreted to represent a fluvial setting.
The first tetrapods appeared in the fossil record over a period, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian 359 mya. The ancestors of all tetrapods began adapting to walking on land, their strong pectoral and pelvic fins gradually evolved into legs (see Tiktaalik). [38]
Stegocephali was re-established to replace the broad definition of Tetrapoda, resolving the usage of two conflicting definitions in discussions of tetrapod evolution. Stegocephali was coined in 1868 by the American paleontologist Edward Drinker Cope , who used it as a general category of prehistoric amphibians.