symplesiomorphy
Technical term in evolutionary biology for an ancestral trait shared by two or more taxa. Used in cladistics and phylogenetics.
Symplesiomorphy is an important concept in phylogenetic analysis.
This trait is a symplesiomorphy, not a derived trait.
Synapomorphy: a shared derived trait, as opposed to the ancestral trait (symplesiomorphy).
Compound of 祖先 (ancestor), 形質 (trait, character), and 共有 (sharing). A direct translation of the English biological term 'symplesiomorphy'.