RT Journal Article SR Electronic A1 Ferreira, Paula Carolina A1 Kava, Vanessa Merlo A1 Aluisio, Rodrigo A1 Alvim Veiga Ludwig, Thelma T1 Frustulia lineata and Frustulia magnifica, two new species of diatom from south Brazil JF Fottea YR 2025 DO 10.5507/fot.2025.002 UL https://fottea.czechphycology.cz/artkey/fot-000000-0591.php AB During studies on the diversity of Frustulia in the state of Paraná, Brazil, two different morphological populations did not correspond exactly to any known described species. This paper describes these species as Frustulia lineata sp. nov. and Frustulia magnifica sp. nov. The samples were collected in lotic environments inserted in the south Brazil Atlantic Forest region. Frustulia lineata sp. nov. is mainly characterized by linear-lanceolate valves with small dimensions, sharing morphological similarities with Frustulia marginata Amossé and Frustulia saxonica f. indica Sarode et Kamat. Frustulia magnifica sp. nov. is significantly larger than other species of the genus, having morphological similarities with Frustulia aotearoa Lange-Bertalot et Beier, Frustulia bahlsii Edlund et Brant, Frustulia rhomboides f. occidentalis Sovereign, and Frustulia sanctarosae Lange-Bertalot et Sterrenburg. Studies using light and scanning electron microscopes have revealed that the morphology and dimensions of the central nodule and the porte-crayon were primary distinguishing features that substantiate the proposal of the new species.