Members of Prochlorophyta have been found as coccoid (spherical) (Coccus) shaped, as in Prochlorococcus, and as filaments, as in Prochlorothrix.
The P. chromatophora symbiont was related to the Prochlorococcus and Synechococcus cyanobacteria (sister to the group consisting of the living members of those two genera).