plesiomorphy; ancestral character
Technical term in evolutionary biology for a primitive trait inherited from a common ancestor, as opposed to a derived trait (apomorphy).
In phylogenetic analysis, it is important to distinguish between ancestral and derived characters.
Derived character (apomorphy), a trait that differs from the ancestral form.
Symplesiomorphy, a shared ancestral trait among a group.
symplesiomorphy
Compound of 祖先 (ancestor) and 形質 (character, trait). A calque from English 'ancestral character' or German 'Plesiomorphie'.