Editing Quadrupedalism (section)

==Quadrupeds vs. tetrapods==
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Although the words ‘quadruped’ and ‘tetrapod’ are both derived from terms meaning ‘four-footed’, they have distinct meanings. A [[tetrapod]] is any member of the [[Linnaean taxonomy|taxonomic]] unit '''[[Tetrapoda]]''' (which is defined by descent from a specific four-limbed ancestor), whereas a quadruped actually uses four limbs for locomotion. Not all tetrapods are quadrupeds and not all quadrupedal animals are tetrapods; some arthropods are adapted for four-footed locomotion, such as the [[raptorial]] [[Mantodea]], or mantises, and the [[Nymphalidae]], or brush-footed butterflies—the largest butterfly family, with ~6000 species, including the well-known [[monarch butterfly|monarch]] (see photo).

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., arms and 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. Even snakes, whose limbs have become [[vestigial structure|vestigial]] or lost entirely, are, nevertheless, tetrapods.