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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.
The classification of tetrapods has a long history. Traditionally, tetrapods are divided into four classes based on gross anatomical and physiological traits. [27] Snakes and other legless reptiles are considered tetrapods because they are sufficiently like other reptiles that have a full complement of limbs.
The group of lobe-finned fishes that were the ancestors of the tetrapod are grouped together as the Rhipidistia, [60] and the first tetrapods evolved from these fish over the relatively short timespan 385–360 Ma. The early tetrapod groups themselves are grouped as Labyrinthodontia.
Tulerpeton is one of the early transition tetrapods – a marine animal capable of living on land. The separation of the pectoral-shoulder girdle from the head allowed the head to move up and down, and the strengthening of the legs and arms allowed the early tetrapods to propel themselves on land. Tulerpeton is important in the study of dactyly.
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 ...
In January 2010, a group of paleontologists published a paper which showed that the first tetrapods appeared long before any know fossils of Tiktaalik or other elpistostegids. [2] This paper was accompanied by extensive supplementary material [3] and also discussed in a Nature documentary on the origin of tetrapods.
Jennifer Alice Clack, FRS, FLS (née Agnew; 3 November 1947 – 26 March 2020) was an English palaeontologist and evolutionary biologist.She specialised in the early evolution of tetrapods, specifically studying the "fish to tetrapod" transition: the origin, evolutionary development and radiation of early tetrapods and their relatives among the lobe-finned fishes.
The earliest known fossilized evidence of bone marrow has been found in Eusthenopteron, which may be the origin of bone marrow in tetrapods. [8] Eusthenopteron foordi. Eusthenopteron shares many unique features among fishes but in common with the earliest-known tetrapods.