– is a trait that cannot be identified as neither a plesiomorphy nor an apomorphy that is a reversal. Reversal – is a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait. Convergence – independent evolution of a similar trait in two or more taxa. Apomorphy – a derived trait. Apomorphy shared by two or more taxa and inherited from a common ancestor is synapomorphy. Apomorphy unique to a given taxon is autapomorphy. Synapomorphy/homology – a derived 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. Autapomorphy – a distinctive derived trait that is unique to a given taxon or group. Homoplasy in biological systematics is when a trait has been gained or lost independently in separate lineages during evolution. This convergent evolution leads to species independently sharing a trait that is different from the trait inferred to have been present in their common ancestor. Parallel homoplasy – derived trait present in two groups or species without a common ancestor due to convergent evolution. Reverse homoplasy – trait present in an ancestor but not in direct descendants that reappears in later descendants. Hemiplasy is the case where a character that appears homoplastic given the species tree actually has a single origin on the associated gene tree. Hemiplasy reflects gene tree-species tree discordance due to the multispecies coalescent. References External links Cladistics, Berkeley Phylogenetics Evolutionary biology terminology de:Apomorphie#Unterteilung von Apomorphien