Editing Forelimb (section)

=== Polydactyly ===
{{See also|Polydactyly in early tetrapods}}

[[Tetrapod]]s were initially understood to have first developed five digits as an ancestral characteristic, which were then reduced or specialized into a number of uses. Certain animals retained 'primitive' forelimbs, such as [[Dactyly|pentadactylous]] (five-fingered) reptiles and primates. This has mostly held true, but the earliest tetrapod or "[[Elpistostegalia|fishapod]]" ancestors may have had more than five digits. This was notably challenged by [[Stephen Jay Gould]] in his 1991 essay "Eight (Or Fewer) Little Piggies".<ref>{{Cite web|url=http://www.stephenjaygould.org/library/gould_eight-piggies.html|title=Stephen Jay Gould "Eight (or Fewer) Little Piggies" 1991|author=Stephen Jay Gould|access-date=2015-10-02|archive-date=2010-01-11|archive-url=https://web.archive.org/web/20100111200502/http://www.stephenjaygould.org/library/gould_eight-piggies.html|url-status=dead}}</ref>

Polydactyly in early tetrapods should 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 tetrapods. Early groups like ''[[Acanthostega]]'' had eight digits, while the more derived ''[[Ichthyostega]]'' had seven digits, the yet-more derived ''[[Tulerpeton]]'' had six toes.

Tetrapods evolved from animals with fins such as found in [[lobe-finned fish]]es. From this condition a new pattern of limb formation evolved, where the development axis of the limb rotated to sprout secondary axes along the lower margin, giving rise to a variable number of very stout skeletal supports for a paddle-like foot.