The Neotropical diversity of spiders is poorly known. Many of the lineages from the Neotropics were described only once; on some occasions, only one of the sexes was known. The sheet weaver genus Diplothyron is one of those groups. We assembled a vast collection of samples and compiled the largest morphological dataset for linyphiids to date. We produced a modern monograph and a new phylogenetic hypothesis for the family. Our study helped to advance the knowledge of the Neotropical diversity of linyphiid spiders and our comprehension of the internal relationships of the lineages.