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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.
Other factors that caused aquatic tetrapods to spend more time on land caused the development of terrestrial hearing with the development of a tympanum within an otic notch and developed by convergent evolution at least three times. [10] There was also a change in the dermal bones of the skull in the aquatic tetrapods. [5]
Archipterygium (or ancient fin) is the concept of a primitive limb from which the limbs of tetrapod animals evolved. The idea was proposed by Carl Gegenbaur in 1878, sometimes termed the gill septum hypothesis and it consisted of a series of rays, one ray large with the remaining small ones attached to the sides of the large one.
Homoplasy (convergent evolution) is considered responsible for several supposedly unique tetrapod features which are also found in non-elpistostegalian Paleozoic fish. The lobe-finned rhizodont Sauripterus has finger-like jointed distal radial bones, [26] [27] while the actinopterygian Tarrasius has a tetrapod-like spinal column with 5 axial ...
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.
One of the persistent questions facing paleontologists is the evolution of the tetrapod limb: specifically, how the internal bones of lobed fins evolved into the feet and toes of tetrapods. In many lobe-finned fish, including living coelacanths and the Australian lungfish , the fin skeleton is based around a straight string of midline bones ...
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).
The evolution of the stapes (from the columella) was an earlier and distinct event. [36] [37] The evolution of the mammalian middle ear appears to have occurred in two steps. A partial middle ear formed by the departure of postdentary bones from the dentary, and happened independently in the ancestors of monotremes and therians. The second step ...