A new Pentaplacodinium species with six precingular plates is described from Bahía Concepción and Bahía de la Paz, Gulf of California. The non-fossil motile stage is described as Pentaplacodinium lapazense, whilst the fossil stage is described as Operculodinium lapazense. The cyst morphology is compared to topotype material of Operculodinium israelianum, which is larger, has longer processes and has a different wall structure. The motile cells display a plate formula of Po, Pt, X, 2′ + *2′, 6′′, 6c, 7 s, 5′′′, 1p, 1′′′′. A typical gonyaulacalean fission line and plate overlap are observed. SSU-ITS-LSU ribosomal DNA sequences demonstrate that Pentaplacodinium saltonense is its closest relative. The species is homothallic. This species occurs in relatively shallow and restricted coastal areas, and has a preference for higher sea-surface temperatures and salinities. MicroFTIR spectra of the cysts are compared to spectra of cysts of other gonyaulacaleans and suggest very similar compositions. No yessotoxins were detected in any of the analyzed strains, hence, this species is unlikely to be responsible for the elevated yessotoxin concentration observed in shellfish on the southern and central coastal region of the Gulf of California.