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Polyphyly

A group cobbled together from two or more separate lineages, lumped by a surface resemblance rather than a recent common ancestor. A polyphyletic group does not even contain the common ancestor of its members - it is a taxonomic basket, not a limb of the tree. Grouping the Na'vi with humans because both stand upright and have two eyes is one example: the resemblance is convergence, and the group built on it collapses the moment real shared derived traits are weighed.