Crown eukaryotes are an artificial group of eukaryotic organisms found at the top of molecular phylogenetic trees including both eukaryotes and prokaryotes. They were originally thought to represent a late step of eukaryotic evolution (somewhat similar to a crown group) because they include multicellular and macroscopic lifeforms that represent the majority of the biomass of the planet while accounting for less than 1% of the genetic diversity. However, they are in fact the result of an artificial clustering of eukaryotic organisms with slowly evolving gene sequences. They are thus not a crown that excludes simpler eukaryotes, but correspond roughly to the initial radiation of eukaryotes. All eukaryotic lineages branching below the "crown" in phylogenetic trees are misplaced because of the long branch attraction phenomenon.
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