Mitochondrial (mt) mRNA editing is a distinct characteristic of dinoflagellates within Alveolata and can be a useful marker to assess whether a lineage of alveolate is a dinoflagellate [12] . RNA editing is a sequence re-tailoring process that can be recognized by changes in an RNA sequence compared to that of its encoding DNA. Initially used to describe the insertion or deletion of uridine residues in mitochondrial (mt) transcripts in the kinetoplastid protozoans, the term ''RNA editing'' now also refers to nucleotide (nt) substitutions in RNA that occur in a wide variety of organisms (see [18] , [19] for review). In Alveolata, mt gene mRNA editing only occurs in dinoflagellates, displaying the greatest diversity of modifications yet described in the context of a single genomic environment. The frequency of editing events decreases from high levels in the late-branching lineages to none in the ancient lineages such as Oxyrrhis and Noctiluca (e.g. [12] , [19] ). It is unclear if Perkinsus spp. mt gene mRNAs undergo editing, but the mt cox1 of P. marinus is not translatable by the standard or mitochondrial codon table. The reading frame must be shifted 10 times by an unknown mechanism to yield a consensus COX1 protein [20] . Once verified, this bizarre process may be used as another molecular feature to demarcate Perkinsus spp. from dinoflagellates.