[2] As of April 2023[update], the Interim Register of Marine and Nonmarine Genera treats the group as a subphylum.

[1] A 2021 review of Euglenozoa places Cavalier-Smith's proposed members of Postgaardia in the class Symbiontida.

[2] Postgaardia are biciliate free-living anaerobes covered in epibiotic bacteria in longitudinal rows are the diagnosis.

A highly contractile pellicle with multiple evenly spaced microtubules and no morphogenetic pairs that are specifically distinguished.

[2] Reconstructions of FA ultrastructure in Postgaardi and Calkinsia confirmed that they were fundamentally similar and deserved to be classified together as a distinct order Postgaardida and class Postgaardea , as both genera share six finger-like projections.