Describing a group that includes an ancestor and some, but not all, of its descendants. These groups are considered artificial because they exclude some evolutionary relatives.
From Greek 'para' meaning 'beside or alongside' and 'phylon' meaning 'tribe or race'. Coined by Willi Hennig in the 1950s to describe incomplete evolutionary groups that traditional classification systems often created by excluding certain descendants.
Paraphyletic groups are like incomplete family reunions - 'reptiles' is paraphyletic because it includes lizards, snakes, and crocodiles but excludes birds, even though birds are just feathered dinosaurs! It's why modern classification is moving away from calling birds 'not reptiles' when they actually are reptiles.
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