The taxonomy of the marine diatom spore genus Liradiscus Greville is established based on detailed light and electron microscopic observations, along with the stratigraphic examination of DSDP Holes 438A, 438B and 436 (northwestern Pacific) and the Newport Beach Section (California). The genus Liradiscus is characterized by circular or elliptical valves covered with circular, branched or net-like veins. Eleven fossil Liradiscus species including five new species (L. akibae, L. japonicus, L. petasus, L. pacificus and L. reticulatus) are described, and their stratigraphic ranges are presented. Liradiscus akibae, L. reticulatus and L. petasus can potentially serve as additional useful biostratigraphic markers to improve the Miocene diatom biostratigraphy of the North Pacific. Furthermore, taxonomy of fossil resting spores will allow us to detect additional paleoceanographic signals recorded in fossil resting spore assemblages in upwelling regions.