Red Algae Beach, Sydney, Australia

Taxonomy
In the system of Adl et al. 2005, the red algae are classified in the Archaeplastida, along with the glaucophytes and green algae plus land plants (Viridiplantae or Chloroplastida). The authors use a hierarchical arrangement where the clade names do not signify rank; the class name Rhodophyceae is used for the red algae. No subdivisions are given; the authors say, "Traditional subgroups are artificial constructs, and no longer valid."
The system reflected the consensus in 2005. Many studies published since then have provided evidence which is in agreement. However, other studies have suggested Archaeplastida is paraphyletic. As of January 2011, the situation appears unresolved.