Samples corresponding to Sporolithon ptychoides Heydrich were collected in the mesophotic zone (50 m depth) south of Espírito Santo State, Brazil. The collected material presented features characteristic of the species, namely: tetrasporangia of 75–105 × 40–55 µm grouped into sori that are raised above the surrounding vegetative thallus surface; presence of a basal layer of elongate cells in areas where the tetrasporangia develop; presence of buried tetrasporangial compartments deep in the thallus; and 3–5 cells in the tetrasporangial paraphyses. These same features said to collectively characterize S. ptychoides, were all observed in a representative specimen and the type specimen of Sporolithon dimotum (Foslie & Howe) Yamaguishi-Tomita ex M.J Wynne. This latter species is thus conspecific with S. ptychoides and is therefore considered a heterotypic synonym thereof, as S. ptychoides has nomenclatural priority. This study expands the known geographical distribution of the species and may give insight into the origin of the species into other geographical regions.