The taxonomic status of Lithophyllum stìctaeforme (Rhodophyta, Corallinales) and its generic position in light of phylogenetic considerations

The type of Lithophyllum stìctaeforme (Areschoug) Hauck (‵ Melobesia stictaeformis Areschoug in J. Agardh) is re‐examined and shown to be conspecific with a common Mediterranean foliose coralline recently recognized as Lithophyllum frondosum (Dufour) Furnari, Cormaci et Alongi (‵ Melobesia frondosa Dufour) and previously known by the misapplied name Lithophyllum (Pseudolithophyllum) expansum Philippi. The generic position of the species in Lithophyllum or Pseudolithophyllum is phylogenetically examined, in the Hennigian sense. It is shown that secondary perithallial outgrowths (‘faux hypothalle’) may represent a synapomorphy for these genera that traditionally have been segregated from each other by the presence, respectively absence, of a coaxial ‘faux hypothalle’. Recognition of both Lithophyllum and Pseudolithophyllum by virtue of a single character in its two states (absent vs. present) is however not tenable, if these genera are considered to be sister‐taxa.