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The zebra is a quadruped. Quadrupedalism is a form of terrestrial locomotion where a
tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes extant and extinct amphibians, reptiles (including dinosaurs and therefore birds), and synapsids (including mammals). Tetr ...
animal uses all four limbs ( legs) to weightbear, walk and run. An
animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, ...
or machine that usually maintains a four-legged posture and moves using all four limbs are said to be a quadruped (from
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became the ...
''quattuor'' for "four", and ''pes'' for "foot"). Most quadrupeds are terrestrial
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...
s, including
mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, females produce milk ...
s and reptiles, though some are largely aquatic such as
turtle Turtles are reptiles of the Order (biology), order Chelonia or Testudines . They are characterized by a special bone, bony or cartilage, cartilaginous animal shell, shell developed from their ribs that acts as a shield. Colloquially, the wor ...
s, amphibians and
pinniped Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, List of semiaquatic tetrapods, semiaquatic marine mammals. They comprise the extant taxon, extant family (b ...
s. Bipedal tetrapods such as some birds like the shoebill sometimes use their wings to right themselves after lunging at prey.


Quadrupeds vs. tetrapods

Although the words ''quadruped'' and ''tetrapod'' are both derived from terms meaning "four-footed", they have distinct meanings. A
tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constituting the superclass Tetrapoda . It includes extant and extinct amphibians, reptiles (including dinosaurs and therefore birds), and synapsids (including mammals). Tetr ...
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 quadrupeds are tetrapods. 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 fins in the case of whales). All of these animals are tetrapods, but none is a quadruped. Even snakes, whose limbs have become vestigial structure, vestigial or lost entirely, are nevertheless tetrapods. Most quadrupedal animals are tetrapods but there are a few exceptions. For instance, among the insects, the praying mantis is a quadruped.


In humans

In July 2005, in rural Turkey, scientists discovered five Kurdish siblings who had learned to walk naturally on their hands and feet. Unlike Common chimpanzee, chimpanzees, which ambulate knuckle-walking, on their knuckles, the The Family That Walks On All Fours, Kurdish siblings walked on their palms, allowing them to preserve the dexterity of their fingers. Many people, especially practitioners of parkour and freerunning and Georges H├ębert's Natural Method, find benefit in quadrupedal movements to build full body strength. Kenichi Ito is a Japanese man famous for speed running on four limbs. Quadrupedalism is sometimes referred to as being on all fours, and is observed in Crawling (human), crawling especially by infants.


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. 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.


Pronograde posture

A related concept to quadrupedalism is pronogrady, or having a horizontal posture of the Torso, trunk. Although nearly all quadrupedal animals are pronograde, there are also bipedal animals with that posture, including many living birds and extinct dinosaurs. Non-human apes with Orthograde posture, orthograde (vertical) backs may walk quadrupedally in what is called knuckle-walking.


See also

* Bipedalism * Orthograde posture


References


External links


Family may provide evolution clue
- BBC News {{locomotion Tetrapods Terrestrial locomotion Articles containing video clips 4 (number), Pedalism