Never before observed or cited in Dinophysis studies, deformations in Dinophysis acuminata and Dinophysis sacculus are reported throughout their cellular division phases (cytokinesis, and sulcal list regeneration) in 5 in situ cell cycle studies in the Punic harbors of Carthage (northern Tunisia). Two types of deformation were observed: invaginations in the ventral and dorsal margin and protuberances at the base of the left sulcal list. No virus or bacteria were detected with Syber green stain. In situ division rates (μ) varied among seasons and stations for the same species. D. acuminata exhibited moderate (0.22 day−1) to high (0.68 day−1) μ rates which were however very low (0.02–0.17 day−1) for D. sacculus in autumn and moderate (0.21–0.35 day−1) in late spring. In 2009 the seasonal distribution of Dinophysis indicates maximum Dinophysis cf. ovum abundance in March and a high number of D. acuminata in early June, while in 2010 maximum abundance of the same species was found in mid-June. Molecular and genetic studies and staining with specific fluorescent strains should be addressed to hopefully explain these Dinophysis cell deformations during their in situ division.