[[Image:Zebra sideview.jpg|thumb|The zebra is a quadruped.]] {{Short description|Form of locomotion using four limbs}} [[File:Brush Foot IMG 1205.jpg|thumb|The monarch butterfly, while a quadruped, is not a tetrapod, but a hexapod. Arrow points to the miniature front leg not used for locomotion.]]
'''Quadrupedalism''' is a form of locomotion in which animals have four legs that are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four legs is a '''quadruped''' (Latin ''quadru-'' 'four' and ''ped-'' 'foot'). Quadruped animals are found among both vertebrates and invertebrates.
==Quadrupeds vs. tetrapods== <!-- Note that Tetrapod may link here. Please bear this in mind, particularly if you are renaming the section. -->
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 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 (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 or lost entirely, are, nevertheless, tetrapods.
== In infants and for exercise == {{main|Crawling (human)}} Quadrupedalism is sometimes referred to as being "on all fours", and is observed in crawling, especially by infants.<ref>Mondschein, Emily R., Karen E. Adolph, and Catherine S. Tamis-LeMonda. "Gender bias in mothers' expectations about infant crawling." Journal of experimental child psychology 77.4 (2000): 304–316.</ref>
In the 20th century quadrupedal movement was popularized as a form of physical exercise by Georges Hebert.<ref>{{cite book |last1=Rathbone |first1=Keith |title=Sport and physical culture in Occupied France: Authoritarianism, agency, and everyday life |date=8 February 2022 |publisher=Manchester University Press |isbn=978-1-5261-5327-2 |page=73 |url=https://books.google.com/books?id=ZidcEAAAQBAJ&pg=PT73 |language=en}}</ref> Kenichi Ito is a Japanese man famous for speed running on four limbs in competitions.<ref>{{cite web|last1=Swatman|first1=Rachel|title=Video: Watch Japan's Kenichi Ito scamper to GWR Day success with fastest 100 m running on all fours|url=http://www.guinnessworldrecords.com/news/2015/11/video-watch-japan%E2%80%99s-kinichi-ito-scamper-to-gwr-day-success-with-fastest-100-m-ru-405713|website=Guinness World Records|location=Tokyo|date=12 November 2015|url-status=live|archive-url=https://web.archive.org/web/20151116012102/http://www.guinnessworldrecords.com/news/2015/11/video-watch-japan%E2%80%99s-kinichi-ito-scamper-to-gwr-day-success-with-fastest-100-m-ru-405713|archive-date=16 November 2015}}</ref>
==Other human quadrupedalism== [[File:CA8-Mutations-Cause-a-Novel-Syndrome-Characterized-by-Ataxia-and-Mild-Mental-Retardation-with-pgen.1000487.s001.ogv|thumb|thumbtime=14|Quadrupedalism in an Iraqi family]]
In July 2005, in rural Turkey, scientists discovered five Turkish siblings who habitually walked on both their hands and feet. Unlike chimpanzees, which ambulate on their knuckles, the Ulas family walked on their palms, allowing them to preserve the dexterity of their fingers.<ref>{{cite magazine |url=http://news.nationalgeographic.com/news/2006/03/0308_060308_all_fours.html |title=Family Walks on All Fours, May Offer Evolution Insight, Experts Say |magazine=National Geographic |date=8 March 2006 |archive-url=https://web.archive.org/web/20160524173648/http://news.nationalgeographic.com/news/2006/03/0308_060308_all_fours.html |archive-date=24 May 2016 }}</ref><ref>{{cite web |url=http://www.huffingtonpost.com/2014/07/17/family-walks-on-all-fours-explained_n_5595462.html |title=Science May Finally Explain Why This Family Walks On All Fours |website=HuffPost |date=17 July 2014 |url-status=live |archive-url=https://web.archive.org/web/20160509060748/http://www.huffingtonpost.com/2014/07/17/family-walks-on-all-fours-explained_n_5595462.html |archive-date=9 May 2016 }}</ref><ref>{{cite journal |vauthors=Türkmen S, Demirhan O, Hoffmann K, etal |title=Cerebellar hypoplasia and quadrupedal locomotion in humans as a recessive trait mapping to chromosome 17p |journal=J. Med. Genet. |volume=43 |issue=5 |pages=461–4 |date=May 2006 |pmid=16371500 |pmc=2564522 |doi=10.1136/jmg.2005.040030 }}</ref>
==Quadrupedal robots==
BigDog is a dynamically stable quadruped robot created in 2005 by Boston Dynamics with Foster-Miller, the NASA Jet Propulsion Laboratory, and the Harvard University Concord Field Station.<ref name="BD">{{cite web |url=http://www.bostondynamics.com/robot_bigdog.html |title=BigDog - The Most Advanced Rough-Terrain Robot on Earth |publisher=Boston Dynamics |access-date=2011-04-06 |archive-url=https://web.archive.org/web/20110423050703/http://bostondynamics.com/robot_bigdog.html |archive-date=2011-04-23 }}</ref> Its successor was Spot.
Also by NASA JPL, in collaboration with University of California, Santa Barbara Robotics Lab, is RoboSimian, with emphasis on stability and deliberation. It has been demonstrated at the DARPA Robotics Challenge.<ref name="RoboSimian">{{cite web |url=https://www-robotics.jpl.nasa.gov/tasks/showTask.cfm?TaskID=236&tdaID=700043 |title=DARPA Robotics Challenge, RoboSimian (Track A) |publisher=JPL Robotics |access-date=2016-03-07 |archive-url=https://web.archive.org/web/20160307163342/https://www-robotics.jpl.nasa.gov/tasks/showTask.cfm?TaskID=236&tdaID=700043 |archive-date=2016-03-07 }}</ref>
== Pronograde posture == A related concept to quadrupedalism is pronogrady, or having a horizontal posture of the trunk. Although nearly all quadrupedal animals are pronograde, bipedal animals also have that posture, including many living birds and extinct dinosaurs.<ref>{{Cite journal|last1=Andrada|first1=Emanuel|last2=Rode|first2=Christian|last3=Sutedja|first3=Yefta|last4=Nyakatura|first4=John A.|last5=Blickhan|first5=Reinhard|date=2014-12-22|title=Trunk orientation causes asymmetries in leg function in small bird terrestrial locomotion|journal=Proceedings of the Royal Society B: Biological Sciences|volume=281|issue=1797|article-number=20141405|doi=10.1098/rspb.2014.1405|pmc=4240980|pmid=25377449}}</ref>
Nonhuman apes with orthograde (vertical) backs may walk quadrupedally in what is called knuckle-walking.<ref>{{cite journal |last1=Gebo |first1=Daniel L. |title=Primate Locomotion |journal=Nature Education Knowledge |date=2013 |volume=4 |issue=8 |page=1 |url=https://www.nature.com/scitable/knowledge/library/primate-locomotion-105284696/ }}</ref>
==References== {{reflist}}
==External links== * [https://news.bbc.co.uk/1/hi/sci/tech/4782492.stm Family may provide evolution clue] - BBC News
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Category:Tetrapods Category:Terrestrial locomotion Category:Articles containing video clips Pedalism