As of the time of writing, one class, 19 families, and two genera are not assigned to any higher ranks. What information is implied by this non-assignment? I presume it is supposed to be understood in one of the two following ways:
- An unassigned taxon is incertae sedis; it may or may not be related to other viral lineages, but further research is needed to make that determination.
- An unassigned taxon represents a unique lineage that has no evolutionary relation to any other viral lineages, but is not assigned to a realm by itself, due to a lack of known diversity or the assignment is pending.
Which is correct?