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The tetrapods, including all large- and medium-sized land animals, have been among the best understood animals since earliest times. By Aristotle 's time, the basic division between mammals, birds and egg-laying tetrapods (the " herptiles ") was well known, and the inclusion of the legless snakes into this group was likewise recognized. [ 28 ]
The distinction between quadrupeds and tetrapods is important in evolutionary biology, particularly in the context of tetrapods whose limbs have adapted to other roles (e.g., hands in the case of humans, wings in the case of birds and bats, and fins in the case of whales). All of these animals are tetrapods, but not all are quadrupeds.
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.
Tetrapods (animals with four limbs) 395 Amniota: Amniotes (fully terrestrial tetrapods whose eggs are "equipped with an amnion") 340 Synapsida: Proto-Mammals 308 Therapsid: Limbs beneath the body and other mammalian traits 280 Class: Mammalia: Mammals: 220 Subclass: Theria: Mammals that give birth to live young (i.e. non-egg-laying) 160 ...
Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the Carboniferous period.
Human taxonomy is the classification of the human species within zoological taxonomy. The systematic genus , Homo , is designed to include both anatomically modern humans and extinct varieties of archaic humans .
Even compared with other social animals, humans have an unusually high degree of flexibility in their facial expressions. [298] Humans are the only animals known to cry emotional tears. [299] Humans are one of the few animals able to self-recognize in mirror tests [300] and there is also debate over to what extent humans are the only animals ...
Today, the 5,500 species of living synapsids, known as the mammals, include both aquatic and flying species, and the largest animal ever known to have existed (the blue whale). Humans are synapsids, as well. Most mammals are viviparous and give birth to live young rather than laying eggs with the exception being the monotremes.