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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]
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.
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 ...
However in a 2008 paper by Boisvert at al. it is noted that Panderichthys, due to its more derived distal portion, might be closer to tetrapods than Tiktaalik, which might have independently developed similarities to tetrapods by convergent evolution. [32] Tetrapod footprints found in Poland and reported in Nature in January 2010 were "securely ...
The vertebrate land invasion refers to the transition of vertebrate animals from being aquatic/semiaquatic to predominantly terrestrial during the Late Devonian period. This transition allowed some vertebrates to escape competitive pressure from other aquatic animals and explore niches on land, [1] which eventually established the vertebrates as the dominant terrestrial phylum.
The legs of tetrapods, the main group of terrestrial vertebrates (which also includes amphibious fish), have internal bones, with externally attached muscles for movement, and the basic form has three key joints: the shoulder joint, the knee joint, and the ankle joint, at which the foot is attached. Within this form there is much variation in ...
The time span of the Phanerozoic starts with the sudden appearance of fossilised evidence of a number of animal phyla; the evolution of those phyla into diverse forms; the evolution of plants; the evolution of fish, arthropods and molluscs; the terrestrial colonization and evolution of insects, chelicerates, myriapods and tetrapods; and the ...