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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.
However, most tetrapod species today are amniotes, most of which are terrestrial tetrapods whose branch evolved from earlier tetrapods early in the Late Carboniferous. The key innovation in amniotes over amphibians is the amnion, which enables the eggs to retain their aqueous contents on land, rather than needing to stay in water.
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.
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]
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]
Lepospondyl and tetrapod classification is still controversial, and even recent studies have had doubts about lepospondyl monophyly. For example, a 2007 paper has suggested that adelospondyls are stem-tetrapods close to colosteids [5] and a 2017 paper on Lethiscus has Aïstopoda in the tetrapod stem based on their primitive braincase. [18]
Anthracodromeus is an extinct genus of Late Carboniferous (late Westphalian stage) "protorothyridid" tetrapods known from Ohio. It is known from the holotype AMNH 6940, a nearly complete skeleton. It was collected in the Linton site in Jefferson County, from the Allegheny Group.
Colosteidae is a family of stegocephalians (stem-group tetrapods) that lived in the Carboniferous period. [1] They possessed a variety of characteristics from different tetrapod or stem-tetrapod groups, which made them historically difficult to classify.