Holophyly

Holophyletic is a term posited as a semantically correct replacement for the term monophyletic as used by cladists (which differs from the usage of evolutionary systematists). It originated amidst confusion over the correct definition for monophyletic group; many definitions were available, of varying degrees of restrictiveness, and holophyletic was posited as a term to describe the definition with scientific utility. The least scientifically useful definition for monophyletic, which is arguably the semantically correct one, considers any group of organisms with a common ancestor to be a monophyletic group. Since it is presumed that one could find a common ancestor from any group of organisms if one goes far enough into the past, this definition implicitly or explicitly constrains what is a legitimate common ancestor, for example by requiring the common ancestor to share a derived trait (synapomorphy) which defines the group.