A distal finger or toe and its corresponding skeletal organization. Positional assignment, morphology and developmental identity must be distinguished when comparing reduced hands.
The thumb is the first digit of the human hand. Its basal joint and muscular control permit opposition toward other fingers, supporting precision grasp. Mobility, orientation and sensory control together explain its function more fully than digit length alone.
The morphological and developmental character identity assigned to a anatomical digit. It is not necessarily equivalent to its ordinal position among the surviving anatomical digits of a reduced limb.
Developmental assignment of position-associated anatomical and molecular character to a digit. A change in digit number or growth is not automatically a homeotic change of identity.
A condition with additional anatomical digits relative to the relevant standard pattern. In early digit-bearing vertebrates, counts above five show that the modern pentadactyl ground plan cannot simply be projected onto the earliest limbs.
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