Abstract We review and revise the taxonomic history of Nitzschia sturionis parasitizing North American Acipenser spp. (sturgeon), and provide data regarding its anatomy. The currently accepted diagnostic character of speciation (hamuli lengths) is unreliable, suggesting the synonymy of Nitzschia superba and Nitzschia monticelli under N. sturionis, resulting in two recognized species of Nitzschia spp. in North America—N. sturionis along the Atlantic coast and Nitzschia quadritestes along the Pacific coast.