Presence of Nemathecia in Parachaetetes Asvapatii Pia, 1936 (Rhodophyta, Gigartinales?): Reproduction in 'Solenoporaceans' Revisited

Parachaetetes asvapatii is a very common algal species in the Palaeogene deposits of the Tethyan realm and has been considered as a member of the heterogeneous family Solenoporaceae. This attribution is exclusively based on features of the vegetative tissue, since no reproductive structures have ever been recovered. However, detailed analysis of Late Cretaceous–Eocene material from Turkey has revealed nemathecia-like structures in one specimen attributable to P. asvapatii. These nemathecia are small wart-like structures protruding on the thallus surface that formed by enlargement of the most peripheral cells of the plant. Nemathecia only occur in three families of the order Gigartinales (Rhodophyta): Rhizophyllidaceae, Peyssonneliaceae and Polyideaceae. Since reproductive structures are stable characters, the presence of nemathecia leads us to tentatively refer P. asvapatii and related species (probably Elianella elegans) to the Gigartinales.