Polydactyly in stem-tetrapods: Difference between revisions - Wikipedia

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{{short description|The state of having more than five digits in ancient fish and tetrapods}}

[[File:Fishapods tetrapods.JPG|thumb|right|500px|Limb evolution: A. ''[[Eusthenopteron]]'', B. ''[[Gogonasus]]'', C. ''[[Panderichthys]]'', D. ''[[Tiktaalik]]'', E. ''[[Acanthostega]]'', F. ''[[Ichthyostega]]'' ( hindleg ), and G. ''[[Tulerpeton]]''. ]]

'''Polydactyly in early tetrapods''' should here be understood as having more than five digits to the finger or foot, a condition that was the natural state of affairs in the very first [[tetrapod]]s during the [[Vertebrate land invasion|evolution of terrestriality]]. The polydactyly in these largely [[aquatic animal]]s is not to be confused with [[polydactyly]] in the medical sense, i.e. it was not an anomaly in the sense it was not a [[congenital disorder|congenital condition]] of having more than the typical number of [[digit (anatomy)|digit]]s for a given [[taxon]].<ref name=hall>''Evolutionary developmental biology'', by Brian Keith Hall, 1998, {{ISBN|0-412-78580-3}}, [https://books.google.com/books?id=JhSwumfgTQ4C&pg=PA262&dq=polydactyly+tetrapods p. 262]</ref> Rather, it appears to be a result of the early [[evolution]] from a limb with a [[fin]] rather than digits.