|Classification and external resources|
Polymelia (from Greek πολυ- = "many" plus μέλος (plural μέλεα) = "limb") is a birth defect involving limbs (a type of dysmelia), in which the affected individual has more than the usual number of limbs. In humans and most land-dwelling animals, this means having five or more limbs. The extra limb is most commonly shrunken and/or deformed.
Sometimes an embryo started as conjoined twins, but one twin degenerated completely except for one or more limbs, which end up attached to the other twin.
Sometimes small extra legs between the normal legs are caused by the body axis forking in the dipygus condition.
- In the summer of 2005, a baby girl named Destiny was born with a fully formed extra leg in Detroit. This was the result of a conjoined twin scenario.
- In March 2006, a baby boy identified only as Jie-jie was born in Shanghai with a fully formed third arm: he had two full-sized left arms, one ventral to the other. This is the only documented case of a child born with a fully formed supernumerary arm. It is an example of an extra limb on a normal body axis. 
- In July 2007 a child was born with four legs at the Lebowakgomo hospital outside Polokwane (South Africa)
- On November 6, 2007, doctors at Bangalore's Sparsh Hospital in Bangalore, India successfully completed surgery on a 2 year old girl named Lakshmi Tatma who was born with 4 arms and 4 legs; but this was not true polymelia but a case of ischiopagus Siamese twinning where one twin's head had disappeared during development.
- Frank Lentini had a third leg.
In other animals
- A four-legged chicken was found by Farmer Skyler Davis of Big D Farms in Winder, Ga during April 2013.
- A four-legged chicken was born at Brendle Farms in Somerset, Pennsylvania, in 2005. The story was carried on the major TV network news programs and USAToday. The bird was found living normally among the rest of the chickens after 18 months. She was adopted and named Henrietta by the farm owner's 13 year old daughter, Ashley, who refuses to sell the chicken. The second (hind) legs are fully formed but non-functional.
- Four-legged ducks are occasionally hatched, such as 'Stumpy', an individual born in February 2007 on a farm in Hampshire, England. See also .
- Frogs in the USA sometimes are affected by polymelia when attacked in the tadpole stage by the Ribeiroia parasite.
- A puppy, known as Lily, was recently[when?] born in the United States with a fully formed fifth leg jutting out between her hind legs. She was initially set to be sold to a freak show, but was instead bought by a dog lover who had the leg removed.
Sleipnir, Odin's horse in Norse mythology, has eight normal horse legs, and is usually depicted with limbs twinned at the shoulder or hip.
Several Hindu deities are depicted with multiple arms and sometimes also multiple legs.
In popular culture
- Edward Albee's stage play The Man Who Had Three Arms tells the story of a fictional individual who was normal at birth but eventually sprouted a third functional arm, protruding from between his shoulder blades. After several years of living with three arms, the extra limb was reabsorbed into his body and the man became physically normal again. In Albee's play, the title character is extremely angry that we (the audience) seem to be much more interested in the period of his life when he had three arms, rather than his normal life before and after that interval.
- Monty Python's Flying Circus performed a skit about a man with three buttocks. (This defect is scientifically possible, though very unlikely.) He believes that he has been invited to be interviewed on television because he is a nice person, and is dismayed to learn that he has only been invited because the interviewer is curious about his unusual condition.
- "Jake the Peg" was a fictional three-legged man, the title of a song played by Rolf Harris in the 1960s. The song was written in 1966 with Frank Roosen, a Dutchman in Vancouver, Canada.
- The Dark Backward is a 1991 comedy film directed and written by Adam Rifkin, which features Judd Nelson as an unfunny garbage man who pursues a stand-up comedy career. When the "comedian" grows a third arm out of his back, he becomes an overnight hit.
- Justice, the main antagonist in the cartoon Afro Samurai, has a fully formed arm protruding from his right shoulder. It is vital to the plot.
- In the film Avatar, most of the creatures have six legs rather than four.
- In the cartoon series Avatar: The Last Airbender, Aang owns a six-legged flying bison.
- Spiral, villain in the X-Men stories of Marvel Comics, has six arms.
- In the Mortal Kombat series, the Shokan is a race of humanoids known to have four arms.
- Ibid: A Life is a fictional biography of Jonathan Blashette, a man with three legs.
- The Associated Press (2006-09-22). "Pennsylvania farm discovers a four-legged chicken". The Associated Press. Retrieved 2006-09-22.
-  MSNBC video of Henrietta
- Avian Diseases, 1985 Jan-Mar;29(1):244-5. Polymelia in a broiler chicken., Anderson WI, Langheinrich KA, McCaskey PC.: "A polymelus monster was observed in a 7-week-old slaughterhouse chicken. The supernumerary limbs were smaller than the normal appendages but contained an equal number of digits.".
- http://www.ncbi.nlm.nih.gov/pubmed/11714039 Polymelia in a calf
- http://www.ias.ac.in/currsci/jun102001/1447.pdf Polymelia in the toad Bufo melanostictus
- Four-legged duckling shocks owner — BBC News, 17 February 2007