The cetacean flipper consists of a soft tissue that encases most of the forelimb containing humerus, radius, ulna, carpals, metacarpals, and phalanges. Several studies have documented the typical cetacean's flipper anatomy, but only a few described digital anomalies and the most common are fusions and supernumerary such as polydactily and polyphalangy. The flippers of the Guiana dolphin, Sotalia guianensis have a falciform general aspect showing individual differences and marks produced by individual contact in social interactions that mainly occur on the posterior border. Here, we report for the first time a case of flippers with anatomical anomalies of loss of digits and deviation of radius of an adult S. guianensis from Baía de Sepetiba (22°54'-23°04', 43°36'-44°02'W), Rio de Janeiro, Southeastern Brazil. Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.