MORPHOLOGY AND TAXONOMY OF EUNOTIA CLEVEI

Abstract

Eunotia clevei Grunow ex Cleve was collected as an epiphyte on aquatic mosses and macroalgae from the Ravdangiin Bulag mineral spring in western Mongolia. E. clevei is widely reported but usually rare in many north temperate large-lake systems and fossil deposits. This taxon is characterized by its large size, two rimoportulae per valve, a small pseudoseptum that is overlapped by die valvocopula, spinules on the dorsal and ventral valve margins, an internal proximal raphe hook, sternum on the valve face, coarsely areolate striae in LM, and epithemioid frustular symmetry (heteropolarity in the transapical plane) because of dorsalty expanded mantles and cingular elements. This combination of characters clearly differentiates E. clevei from Eunotia sensu stricto;, however, some of these characters are shared with other eunotioid genera such as Desmogonium, Semiorbis, Peronia, Actinella, and Eunophora, suggesting that Eunotia clevei, its varieties, and allied taxa may be better placed within a new genus.