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An autapomorphy in cladistics is a derived trait or apomorphy that is unique to only one terminal group. That is, it is found only in one member of a clade, but not found in any others or outgroup taxa, not even those most closely related to the group (which may be a species, family or in general any clade).

An autapomorphy is not present in the closest relative of the terminal group and also was not present in their common ancestor.

See also[]

  • Homoplasy – a trait that is found in several terminal groups but evolved independently (i.e., was not present in their common ancestor)
  • Synapomorphy – a trait that is found in some or all terminal groups of a clade, and inherited from a common ancestor, for which it was an autapomorphy (i.e., not present in its immediate ancestor).
    • Underlying synapomorphy – a synapomorphy that has been lost again in many members of the clade. If lost in all but one, it can be hard to distinguish from an autapomorphy.


Cladistics
· Apomorphy · Clade · Cladistic controversies · Cladistic methodology · The cladistic revolution · Cladistic taxonomy · Cladogram · Fundamental concepts of Cladistics · Synapomorphy · PhyloCode ·


Mantell's Iguanodon restoration
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