Topic summary
Pentadactyly
Extracted from the Wikipedia article Dactyly.
Pentadactyly
Pentadactyly (from Ancient Greekπέντε (pénte), meaning "five") is the condition of having five digits on each limb. It is traditionally believed that all living tetrapods are descended from an ancestor with a pentadactyl limb, although many species have now lost or transformed some or all of their digits by the process of evolution. However, this viewpoint was challenged by Stephen Jay Gould in his 1991 essay "Eight (or Fewer) Little Piggies," where he pointed out polydactyly in early tetrapods and described the specializations of digit reduction. Despite the individual variations listed below, the relationship is to the original five-digit model.