Taxonomic reassessment of C hondrus verrucosus ( R hodophyta, G igartinales), with a description of C hondrus retortus sp. nov

Summary Phylogenetic and morphological reinvestigation of C hondrus verrucosus   M ikami was conducted in the P acific coast of southeastern H onshu, J apan, including the holotype specimen and samples near the type locality. Two entities were recognized by phylogenetic analyses of plastid rbc L and nuclear EF2 sequences. In morphological analyses, the two entities were distinguished by: (i) thallus size and form, and (ii) cell shape of the medullary layer surrounding young carposporangia: one has larger thalli, is regularly canaliculated, with linear medullary cells (large‐type); the other is smaller, canaliculated with crispation and has roundish medullary cells (small‐type). The large‐type was common in southern to eastern B oso P eninsula including near the type locality; the small‐type was typical in the southwest B oso P eninsula and S agami B ay. The large‐type was shown to be equivalent to C . verrucosus by examination of the holotype specimen. The small‐type is described as a new species, C . retortus   M atsumoto et S himada.