Taxonomic and biostratigraphical re-assessments of Subterraniphyllum Elliott (Corallinales, Rhodophyta)

A taxonomic and biostratigraphical re-assessment of Subterraniphyllum Ellio tt (Corallinales, Rhodophyta) is presented. Results from studies of the typ e collection and of newly collected material from north-eastern Italy and n orthern Slovenia have shown that this taxon is not a geniculate coralline r ed alga as originally suggested by Elliott and most subsequent authors. Veg etatively, Subterraniphyllum most closely resembles certain living members of the Corallinales; however, the phenetic and phylogenetic relationships o f Subterraniphyllum to other Corallinales cannot be determined with greater certainty. The exclusion of Subteranniphyllum from any group of Corallinac eae with genicula is based on unequivocal evidence that branch formation do es not involve the occurrence of genicula. Subterraniphyllum seems to be re stricted to the Oligocene. Reports of occurrences in Upper Eocene and Lower Miocene sediments cannot be substantiated. Subterraniphyllum, however, can not be considered a useful stratigraphical marker until further data on its occurrence in well-dated carbonate sequences are acquired. This study illu strates the problems associated with placing fossil coralline algal specime ns into geniculate genera without the preservation of relevant morphologica l characters. This is especially true in the absence of the careful assessm ent of fossil material with respect to current taxonomic concepts of genicu late coralline genera, all of which are based on studies of living species. According to the current concepts for geniculate coralline genera, the pla cing of fossil specimens into geniculate genera without appropriate evidenc e must be avoided by grouping all potentially geniculate fragments under th e informal group 'Geniculate sensu lato'. Furthermore, for all those many f ossil specimens where unequivocal evidence is not present, it is possible t o utilize 'form genera' based on characters that are normally preserved. Th is leads to creating a consistent, workable system of applying names to mos t fossil corallines so that they can be reliably used in relation to strati graphical and palaeoecological studies.