A taxonomic and nomenclatural reassessment of Tenarea, Titanoderma and Dermatolithon (Corallinaceae, Rhodophyta) based on studies of type and other critical specimens

Abstract

The taxonomy and nomenclature of genera of the Tenarea/Dermatolithon complex has been reassessed on the basis of a study of generitype and other critical specimens. The type specimen of Millepora tortuosa Esper, which is the type of Tenarea Bory 1832, proves to be conspecific with the specimen on which Bory based his description of the genus. Tenarea undulosa Bory is an illegitimate name for T. tortuosa (Esper) Lemoine rather than an independent species. Since 1898, M. tortuosa has been incorrectly associated with the alga that is the principal component of the ‘trottoirs’ (coralline pavements) of the western Mediterranean. This alga is referable to Lithophyllum lichenoides Philippi. Titanoderma Nageli 1858 is an earlier homotypic synonym of Dermatolithon Foslie 1898, both being based on Melobesia pustulata Lamouroux. Titanoderma, in view of its clear record, is adopted in preference to proposing Dermatolithon for conservation. Tenarea comprises a single species of Lithophylloideae in which the thallus is composed of erect or ascending lamellae whose vegetative tissues are organized in an isobilateral manner and include a medulla of two layers of palisade cells. Titanoderma (syn. Dermatolithon) encompasses those Lithophylloideae in which the thallus consists largely or entirely of a prostrate crust whose tissues are organized in a dorsiventral manner and include a unistratose hypothallium composed of palisade-like cells. Titanoderma includes at least 16 species.