The following taxon apparently lies within the circumscription of Pleonosporium borreri but has not yet been transferred or reduced to synonymy:
Callithamnion borreri (J.E. Smith) C. Agardh var. elongatum Kützing, 1849: 643 (type locality: England).—Hadi et al., 1993: 128, figs. 39, 79.
INDIAN OCEAN DISTRIBUTION: Iraq.