Résumé
A new fossil diatom species of Encyonema K & uuml;tzing was collected from the Pleistocene sediments of Col & ocirc;nia basin, State of S & atilde;o Paulo, Southeast Brazil, as part of an ongoing survey of its sedimentary record, aiming at exploring the long-term evolution of the Southern Hemisphere lowland rainforest. Morphology of the new species was examined using both light and scanning electron microscopy, and compared with the morphologically closest species in the genus, Encyonema latum Krammer and E. macedonicum Z.Levkov, D.Metzeltin and S.Krstic. The new species is characterized by a distinctly dorsiventral valve outline, a nearly straight ventral margin, and a relatively low length-to-width ratio, along with a higher areolae number. Preliminary diatom analysis of the Col & ocirc;nia basin sedimentary record indicates that the new species occurred associated with high organic matter input and shallow lake conditions, during a cold and humid period. The study contributes to the understanding of the Col & ocirc;nia basin biodiversity and will assist future ecological and evolutionary studies in the region.