Topic summary
Autapomorphies
Extracted from the Wikipedia article Autapomorphy.
Background
Because autapomorphies are present only in a single taxon, they do not convey information about relationship. Therefore, autapomorphies are not useful to infer phylogenetic relationships. However, autapomorphy, like synapomorphy and plesiomorphy is a relative concept depending on the taxon in question. An autapomorphy at a given level may well be a synapomorphy at a less-inclusive level. An example of an autapomorphy can be described in modern snakes. Snakes have lost the two pairs of legs that characterize all of Tetrapoda, and the closest taxa to Ophidia – as well as their common ancestors – all have two pairs of legs. Therefore, the Ophidia taxon presents an autapomorphy with respect to its absence of legs.