 A 2013 study summarized the state of potential Ornithocercus phylogeny and placed them in clade with "Citharistes" and "Histioneis" with which the ectosymbiontic feature is shared.This indicates that a common ancestor of these genera likely gained this relationship with cyanobacteria.Both "Ornithocercus" and "Histioneis" have cyanobacteria living between cingular lists whereas "Citharistes" have their ectosymbionts in a dorsal girdle-chamber.