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A tetrapod (/ ˈ t ɛ t r ə ˌ p ɒ d /; [5] ... Skin breathing, known as cutaneous respiration, is common in fish and amphibians, and occur both in and out of water ...
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 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 ...
The tetrapods, a mostly terrestrial superclass of vertebrates, are now recognized as having evolved from sarcopterygian ancestors and are most closely related to lungfishes. Their paired pectoral and pelvic fins evolved into limbs, and their foregut diverticulum eventually evolved into air-breathing lungs.
When breathing air, the spiral valve of the conus arteriosus closes (minimizing the mixing of oxygenated and deoxygenated blood), the third and fourth gill arches open, the second and fifth gill arches close (minimizing the possible loss of the oxygen obtained in the lungs through the gills), the sixth arteriole's ductus arteriosus is closed ...
The first tetrapods are four-legged, air-breathing, terrestrial animals from which the land vertebrates descended, including humans. They evolved from lobe-finned fish of the clade Sarcopterygii , appearing in coastal water in the middle Devonian, and giving rise to the first amphibians .
In tetrapods the spiracle seems to have developed first into the otic notch of early tetrapods where it was still used in respiration and incapable of sensing sound, [13] [14] and then into the ear of modern tetrapods which by the Eustachian tube remains connected to the buccal cavity. [15]
Several groups of tetrapods have undergone secondary aquatic adaptation, an evolutionary transition from being purely terrestrial to living at least part of the time in water. These animals are called "secondarily aquatic" because although their ancestors lived on land for hundreds of millions of years, they all originally descended from ...