Comparative ultrastructure of two closely related thalassiosira species: Thalassiosira vulnifica (gombos) fenner and T. fasciculata Harwood et Maruyama

The distinctive morphology and relatively short geological range (3.25 to 2.5 Ma) of Thalassiosira vulniflca (Gombos) Fenner make it especially useful for Pliocene biostratigraphic studies in the Antarctic region. Thalassiosira fasciculata Harwood et Maruyama has a geological range (4.5 to 0.75 Ma) that overlaps that of T. vulnifica and it resembles this taxon in possessing prominent fultoportulae on the valve face, strongly fasciculated areolae, and distinctive marginal fultoportulae. However, the greater spacing between rows of areolae and the larger distinctive fultoportulae present in T. vulnifica clearly separate it from T. fasciculata. The importance of accurate identification is discussed as it relates to ongoing Antarctic glacial sediment studies.