Burliganiella gen. nov. (Bacillariophyta, Eunotiales): Another Case of Raphe Reduction Based on the Type Material of Fragilaria siolii Hustedt

Abstract A new monotypic diatoms genus from Brazil is described based on gatherings and descriptions from the Amazon made by Hustedt in the early 50's. Burliganiella gen. nov. is described using light and scanning electron microscope and has as generitype Burliganiella siolii (Hustedt) comb. nov., originally described within Fragilaria Lyngb. The main diagnosed features include valves slightly asymmetrical to the apical axis with a sternum located near the ventral margin (Eunotia-like) while internally having slits that are not associated with a helictoglossa and no rimoportula (which is completely absent). While some characters link the species to the ‘araphid’ genus Fragilariforma D.M. Williams & Round, Burliganiella has more shared characters with the Eunotiales. For instance, the lack of a raphe in other species of eunotioid diatoms, suggests multiple lineages within the Eunotiales have reduced or lost raphe systems, such as in the case of Burliganiella.