Zur revision der gattung Achnanthes sensu lato (Bacillariophyceae): Achnantheiopsis, eine neue gattung mit dem typus generis A. lanceolata

This contribution to the revision of the genus Achnanthes sensu lato concerns a section of 38 apparently closely related taxa. Neither do they fit into Achnanthes sensu stricto with the type species A. adnata (syn. A. brevipes) nor into Achnanthidium with type species A. microcephalum (syn. A. minutissima). They also do not conform with the morphologic pattern of Eucocconeis or of the recently described Psammothidium. The proposed new genus Achnantheiopsis is characterized by a unique complex of distinct features. These are represented in particular by the most prominent species respectively species clusters around A. lanceolata and A. delicatula.