This study shows that in Bottlenose dolphins and in Harbour porpoises the presence of marginal papillae is age related. In Bottlenose dolphins the papillae disappear around the age of 16 years. A 6-year-old Commerson’s dolphin also showed remnants of marginal papillae on its tongue. Histological examinations of the papillae of a young Harbour porpoise showed that they are composed of thick fiat multi-layer epithelium with probably a high level of cell multiplications. Based on these findings a dual function of the papillae is suggested: the papillae keep the milk from seeping from the buccal cavity during the suckling period, and later in life, when the animal starts eating fish, they aid in feeding. Before swallowing, the water surrounding the fish is squeezed out of the buccal cavity, and the papillae prevent water from re-entering this cavity.