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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.
Tetrapoda. See also below. Tetrapodomorpha (also known as Choanata[3]) is a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish. Advanced forms transitional between fish and the early labyrinthodonts, such as ...
The choanae (internal nostrils) of a cat, indicated by the dashed lines and bounded by the vomer (blue gray) and the palatine bone (orange). The choanae (sg.: choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the pharynx, in humans and other mammals (as well as crocodilians and most skinks).
Tetrapod. A tetrapod (/ ˈtɛtrəˌpɒd /; [5] from Ancient Greek τετρα- (tetra-) 'four' and πούς (poús) 'foot') is any four- limbed vertebrate animal of the superclass Tetrapoda (/ tɛˈtræpədə /). [6] Tetrapods include all extant and extinct amphibians and amniotes, with the latter in turn evolving into two major clades, the ...
Kenichthys was a small tetrapodomorph, with a skull about 2 centimetres (0.79 in) long. [3] While only areas of the front of the body are known, it seems likely that Kenichthys would have been similar in general body form to other basal sarcopterygians, with two dorsal fins, paired pectoral and pelvic fins and an anal fin.
Until finds of other early tetrapods and closely related fishes in the late 20th century, Ichthyostega stood alone as the transitional fossil between fish and tetrapods, combining a fishlike tail and gills with an amphibian skull and limbs. It possessed lungs and limbs with seven digits that helped it navigate through shallow water in swamps.
Skeletal changes of vertebrates transitioning from water to land. Innovations conventionally associated with terrestrially first appeared in aquatic elpistostegalians such as Panderichthys rhombolepis, Elpistostege watsoni, and Tiktaalik roseae. Phylogenetic analyses distribute the features that developed along the tetrapod stem and display a ...
Together, these taxa form the Dipnomorpha, the sister group to the Tetrapodomorpha. Together, these form the Rhipidistia , the sister group to the coelacanths . Recent molecular genetic analyses strongly support a sister relationship of lungfishes and tetrapods ( Rhipidistia ), with coelacanths branching slightly earlier.