Amphicocconeis ruatara, Riaux-Gobin & Garcia & Witkowski & Saenz-Agudelo & Coste & Daniszewska-Kowalczyk, 2021

Riaux-Gobin, Catherine, Garcia, Marinês, Witkowski, Andrzej, Saenz-Agudelo, Pablo, Coste, Michel & Daniszewska-Kowalczyk, Genowefa, 2021, New Amphicocconeis (Bacillariophyta) from Raivavae and Tahiti Islands (South Pacific) and Porto Belo (Brazil), with re-examination of Psammococconeis, Phytotaxa 513 (1), pp. 30-54 : 40-43

Remarks on Psammococconeis disculoides (Hustedt) sensu M.Garcia and Amphicocconeis disculoides (Hustedt) De Stefano & Marino

Following De Stefano & Marino (2003), ‘the main differences between Amphicocconeis and Psammococconeis are the presence of the following additional characters in Amphicocconeis disculoides (op. cit.: table 1): (i) external raphe endings with terminal fissures (op. cit.: fig. 22), (ii) a single kind of mantle areolae (op. cit.: figs 2, 8) and (iii) SV and RSV (raphe sternum valve) areolae occluded by smooth hymenes without fimbriae (op. cit.: figs 4–5, arrow, 25, 27–29) and rectangular clusters of perforations in the SV valvocopula (SVVC) (op. cit.: figs 16, 19)’.

About the aforementioned additional characters in Amphicocconeis , some remarks can be afforded: In Garcia (2001), the terminal raphe endings are not clearly illustrated (op. cit.: figs 12, 15, 17–18; LM and SEM), the same remarks can be made about Psammococconeis brasiliensis (op. cit.: figs 1–11). Furthermore, the presence of two kinds of SV areolae on the margin: as remarked in Riaux-Gobin et al. (2011), ‘the more or less triangular or short rounded kind of marginal structure ( Garcia 2001: figs 10, 21, 23) does not seem to be true areolae, but rather small depressions in the valve wall’, but ‘this alternation of areolae and depressions along the SV margin seems characteristic of Psammococconeis , being observed in the two species known in the genus’. Another remark concerns the ‘fimbriae’ observed on the SV areolae ( Garcia 2001: figs 23) and RV areolae (op. cit., fig. 25), that are outgrowths (or flaps) of the virgae (op. cit., ‘valve areolae occlusion located below the valve surface and containing fimbriae’), not prejudging the existence of a true hymen below these outgrowths.

Lastly, the SVVC was neither found nor detailed in Garcia (2001).