Surirella prespanensis sp. nov. and Surirella hinziae sp. nov., two new diatom (bacillariophyceae) species from ancient lake prespa (macedonia/albania/greece)

3 Institute of Biology, Faculty of Natural Sciences, Arhimedova 3, 1000 Skopje, R. of Macedonia Abstract: Surirella is a polyphyletic and highly diverse diatom genus with more than 500 species described worldwide. Within a study of its diversity and distribution in the Republic of Macedonia, ancient Lake Prespa has been investigated, as "sister" to Lake Ohrid and part of a unique lake system with extraordinary age, biodiversity and number of endemic species. During the study, two new Surirella species have been identified and their LM and SEM based formal descriptions and differential diagnoses are provided herein. Surirella prespanensis sp. nov. has been observed in the contemporary and the fossil diatom flora of the lake. It can be distinguished from other similar taxa by its valve outline, size, shape of the median ridge and the presence of silica grooves along the raphe. Surirella hinziae sp. nov. is known only from the fossil diatom flora of Lake Prespa and can be recognized by its valve outline, size, shape of the median ridge and the presence of helictoglossa-like processes.